I can tell (basing on my own experience), that if you're very fond of some genre/sub-genre and some title/series/character, it's worth a shot (in most cases). I've read many negative opinions about such games as StC 4 (mostly Ep1) or (not so many, but still) Sonic Heroes... And in practice I've enjoyed Sonic Heroes more than both Sonic Adventure titles, and first episode of StH 4 was for me quite easy, but pleasant experience (well, not counting the last level :P). Not to mention about other games/franchises (for example, I've spent a lot time with Resident Evil 6, which didn't have too good opinions).
I didn't have experience with Sonic titles which are considered as "really bad", such as Sonic 06 (lack of console), but if it's not about buggy and technically underdeveloped product, I would give a chance for title, which is making me curious, even with quite bad reviews. So I would recommend at the beginning to read about the technological lacks, because well, they're one of these rare things, which can be considered in case of games as "indisputable disadvantages").
Basing on my experience with "questionable" Sonic titles, I can recommend without hesitation Sonic Heroes, Sonic Riders (although this one is a bit tricky, you'll need to get used to specific gameplay) and Sonic the Hedgehog 4 (both episodes).
This post has been edited by MartiusR: 27 January 2015 - 06:39 AM