Bottom one, simply because of the multiple colours. You'll notice that sonic games tend to use a mixture of colour for titlecards (Take a look at sonic 2 for example), of course that doesn't mean to say I don't like the top one, that one's nice and even, and seems less odd. I would suggest giving a bit more contrast to the bottom one, give it a bit more colour/life. That's just my opinion though. EDIT: quick paint moc-up (Not brilliant, but there for an example):
I like both... If only there was a way to use both of them in some way... Maybe the gray one at the beginning, and then switch to the colored one once you unlock something, I don't know... Apply color to one of the elements when you collect a chaos emerald?
Or better yet, have the title card assemble itself while gray, then slowly fill in and/or fade in to the colored version before displaying the level and having the title card exit.
Sorry but that thing is ugly. It just depends on how you want to go Hez the grey is kind of modern and the colored one is more retro. As you can tell by my fan game I'm a big fan of retro sonic game play but some things need a bit of updating... Oh and DalekSam do you have a picture of the Sonic 3D tile I do not recall it.
If you are going to do color Hez I suggest going with dark colors and only use maybe 2 color that bottom strip can easily be a semitransparent black to give it some depth.
I sort of updated Luster Lakes...background is more dark. It makes the forground stick out more. I also changed it to a blue tent instead of a purple. I may also change the water color. Not sure yet. Better? Worse?
Could you provide some other screenshots for comparison between the old version and the new one, please?