OK, this thread is to discuss about games that really break the limits of the systems they were made for. By this I don't mean that they just look impressive, but that outright look like there's absolutely no way they could be running on that thing no matter what (yet obviously somebody figured out how). Basically games that look like they actually belong to a later generation than the system on which they run.
First I'll start with Red Zone. The entire game is pretty much demoscene so it's not surprising =P I find the indoor areas more interesting than the outdoor ones, even though technically they aren't as impressive (a lot of it is just the video hardware doing its job). They don't feel as empty and honestly, they look like they could have come out of the early GTA games. Same perspective, even. Seriously:
Then there's... this. Road Rash on the Master System and Game Gear (both are based off the same code). You can tell only because the sound gives it away (shame the FM add-on was pretty much dead by that point), otherwise it's essentially indistinguishable from its 16-bit counterparts. In fact, I compared its framerate against the Mega Drive, and this version is actually faster (5~6 frames per tick as opposed to 6~8), although of course it lacks the sprite scaling so that's probably how it gets away with it. And before somebody points out that the road could be done by just changing the scroll mid-line: you can't do this with the vertical scrolling on this system (only horizontal). Hills are software rendered. Only the curves could be done with scrolling.
And finally for this post, Wacky Races for the Game Boy Color. That's one trollish video title, it says GBA. Then again, given how that road looks like and how colorful is the background, it isn't surprising, it could really pass for GBA if it wanted. That the steps between sprites is so smooth doesn't help either. Again, sound gives it away (not much that can be done about this in this case, sadly).
What games would you mention? Remember, they can't be just impressive, they need to look outright impossible.