Robotnik as a Heartless Monster
These portrayals of Robotnik focus on a character who's more monster than man. He has little, if any, redeeming qualities and has a heart as cold and unfeeling as his machines.
SatAM's Robotnik
He's big, bad, and mean! A staple of early 90s Sonic media, Julian was a drastic redesign on the quirky and lovable Eggman of the games. His intimidating appearance, complete with eery glowing eyes and a robotic arm, are just the tip of the pointy-headed iceberg when it comes to how genuinely terrifying this man was to his enemies. The process of roboticization is a fairly creepy interpretation of the cutesy Badniks, and it was a feared fate worse than death for the show's cast. This guy was no-nonsense, and the only hints of a soft side we saw were for his robotic pet bird, Cluck; Not even family member Snively could ever get on Robotnik's good side, and that's going on the blind assumption there was a good side to begin with.
Archie - Robotnik Prime
Despite being inspired by SatAM, Archie's Robotnik was a vastly different character. He was still evil. He still roboticized his captives. But he was far more pro-active in that he actually invented mechs and machines on a regular basis instead of calmly sitting around in his base. Despite the change-up in approach and slightly more comical personality, however, there was little good to be seen in his motives.
Fleetway's Robotnik
After the truly tragic origin story of going from the kindly Dr. Kintobor to the murderous Dr. Robotnik, the extent of this Robotnik's evil dwarf even SatAM's. Don't be fooled by his resemblance to his slapstick-happy AoStH counterpart; The two couldn't be more different, as Fleetway's devious doctor uses an equally creepy re-interpretation of the Badniks; Rather than re-engineering animals into robots, they're hooked into machines and power them as living batteries until they die, and there's no discrimination between common animals and the sentient humanoid ones in this case. His cruelty is only matched by his madness; Causing rampant destruction and chaos everywhere he goes, the transformed Kintobor's tragic tale leads to a maddening attempt to destroy everyone, including himself. Without spoiling how it turns out, it truly demonstrates the extent of how absolutely crazy he is. Still, he wasn't without his supporters. Aside from his loyal assistant Grimer, the Dr. Robotnik Appreciation Tribe(D.R.A.T.) consisted of a small cult-like following that supported his planetary rule.
Robotnik as Evil, But Not Entirely Unsympathetic
A big distinction between this and the above category is that these Robotniks- whilst unambiguously evil- aren't sadistic and torturous. The pain they cause is more like a side effect of their selfish desires for conquest than something they inflict just for the hell of it.
AoStH's Robotnik
After a childhood of being raised by a maddening woman who advocated evil as one of life's most important virtues, it's no surprise Robotnik ended up a rather rotten fellow. Still, there's some depth to be seen here, which is saying something considering the usual lack of complexity of this series. Aside from being a product of how he was raised, this Robotnik's been motivated by love several times. Being rejected by his highschool crush, Lucinda, was the very catalyst that drove him to quit school and launch his villainous career, where for 30 years he continued to brood over his love lost- He'd go on to build a robotic wife that malfunctioned due to water exposure later. It can also be said that this Robotnik enjoys a sense of comradery with his lackeys; Though he usually berates them for their failures, the few times they do something right are almost always met with words of praise and appreciation from their master. In this way, although Robotnik is an evil man, he's not without his nicer points, and beyond his promotion of rottenness and declarations of hatred lies a man who just wants love and attention.
Sonic Underground's Robotnik
This Robotnik uses roboticization, much like his SatAM counterpart. But he's not nearly as cold and unmoving; A good portion of Mobius was left as is, and continue to live in relative comfort, if not denied of civil liberties and subject to unfair taxes. Like AoStH's Robotnik, Underground's Doctor has a sense of friendship with his henchmen, and is prone to idle friendly banter with his hired hands, Sleet and Dingo, at times.
Sonic OVA's Robotnik
This one is almost Anti-Villain territory, but his engineered apocalypse plans kind of rule him out on that. Still, aside from wanting to destroy the entire Land of the Sky and everyone in it, there's a bit of depth here, and like AoStH, it's romantic in nature. Blatantly and unashamedly in love with the president's daughter Sera, Eggman shows genuine concern for her safety and well-being throughout the plot, and even agrees to her demands to pursue Sonic in the end.
Archie - Robotnik Mk. II (Eggman)
Now, this is an interesting one. According to current writer Ian Flynn, this Robotnik had essentially the same history from his dimension as did Robotnik Prime; The exception being he defeated his Sonic and eventually moved on to the comic's primary dimension to conquer its Mobius. So why is he here instead of the "Heartless monster" category?
Well, he's developed since then. He entered the comic as a sadistic and deplorable fellow who took great enjoyment in causing others pain and suffering. But over the span of many issues, he's been "humanized" in more ways than one; In addition to transforming from robotic to organic form, he's explored deeper sides of his personality. He tried to create a surrogate family for himself in the form of M and ADAM, and actually tried- for a while at least- to be a father figure of sorts to them. In addition, before a huge attack on Knothole, he offered Snively a chance to rejoin his cause, and in general, he gets along with him and respects him a bit more than he used to, and certainly more than the first Robotnik did. He's also been willing to team up with Sonic to destroy greater enemies, and while this can be considered self-preservation, he's usually honorable during these truces.
Robotnik as an Anti-Villain
These are the Robotniks who are genuinely good people, deep down. Despite their penchant for selfish behavior and wanton destruction, they're portrayed with a sense of morals that they refuse to compromise, and because of this, they don't really see themselves as evildoers. Simply; An antihero is a hero who does evil or morally-questionable things. An antivillain is a villain, then, who does good things.
SEGA's Robotnik
Misguided yet well-intentioned extremist. That's the best way I can describe the Eggman of the games. He wants to conquer the world and create what he's on multiple occasions described as a utopia, Eggmanland. His chivalry and respect for his opponents is more evident here than in any other continuity; SA2 states very plainly that he considers Sonic a most admirable adversary, and clearly he respects him for his determination. Similarly, Tails earns his respect as an inventor in Chronicles. But more than mere respect and gentlemanly mannerisms is Eggman's conscience.
SA2 shows this, again. He looked up to Gerald throughout childhood, and considered him a great and honorable man; He was taken aback and noticeably disappointed when he discovered his grandfather's dark intentions. During the Devil Doom battle in Shadow the Hedgehog, if you wait long enough, Eggman will confess that he lied about Shadow's identity and apologize for lying. Why would he do that, if it serves no benefit to his schemes? He wanted to make things right, and simply felt guilty for his deceit.
He's definitely got a very strong good side, but as the manual to Sonic Heroes states, "his charms are often difficult to spot through the abominable laughter that accompanies his maniacal declarations of world domination."
Sonic X's Robotnik (Anime)
Take Sega, give him friends to hang out with(In the form of his henchmen), have him more vocally express his opposition to injustice, and you've got Sonic X's nearly heroic take on Eggman. All the above good points from Sega apply, plus these!
He openly says that harming hostages is wrong, berating the Metarax for their crass methods and reliance on needless destruction. In very blatant wording, he describes his sense of honor and insults them for their lack of the same.
He also cares about his robots' well-being, and seems to treat them more like friends than lackeys- When Decoe and Bocoe temporarily run away, he tries to cook Bokkun breakfast, with questionable results. Still, he tried.
And even though I dislike Chris as a character, the little brat was useful for his character development, leading to Eggman giving the boy anecdotes about his own life experiences, and ultimately helping him cope with harsh, inevitable reality.
I think that Sonic X's Eggman is a good person who just happens to do bad things, like the odd take-over-the-world plot on occasion.
Sonic X's Robotnik (Comics)
And if the anime's Eggman wasn't heroic enough, how about this? If any Eggman could believably reform, it'd be this one.
During the El Gran Gordo arc, we see that his real motivation is to be loved by the masses. That's all he wants; To be appreciated and praised. And with the support of his fans, he almost beats Sonic in a head-on match, and actually does defeat the hulking wrestler Andes the Ginormous. He wistfully becomes conflicted with his identity, wondering what it would be like to escape to a life of public adoration and heroism.
When his body gets swapped with Sonic's, he doesn't use his position to do evil things; Quite the contrary, he actively tries to save the president, and enjoys the praise and glamor of the hero's life for a day. And recently, he sends a giant Bokkun out to help neutralize the (over-exaggerated) threat of gigantic Vector, hoping people will take notice of, well, all the good he's doing so that they'll praise him and shower him with affection.
Really, this Eggman's kind of a spastic hero-villain combination. He'll fight Sonic on occassion, but he hasn't tried to actively conquer the city or cause any notable mischief since early on, when the series was just starting out. While he's never "officially" reformed, this Eggman's actively doing more good than evil, and is even starting to enjoy the public image of being a hero. The little romantic subplot with Ella was a nice expansion of his personality as well.
Conclusion
As we've seen, this man's been portrayed in an amazingly vast variety of ways. Even within the categories I've presented, you could divide them into more categories. But what do you think?
Do you prefer an Eggman who's heartlessly evil? Heroic yet misguided? Or some nice middleground between the two?
Me? While I do like all Robotniks, personally, my favorites are ones with an Anti-Villain approach. I find them, especially the Sonic X comic's, to be truly good people that are incredibly easy to sympathize with. It's a nice dynamic, in that despite his selfish actions, he really does have a well-developed good side to keep himself in check. Of course, darker takes on Robotnik can be fun too sometimes, but I prefer it when he's nice on the inside.

