Road Rash 32 is the best ever, it beats the crap out of the 3D versions. Worms is also another great 2D game (what happened to Team 17? They seem to only do Worms now, as much as Core Design only do Tomb Raider... at least Core recently made a game without Lara Croft)
I believe incredible light and color effects are possible today in 2D, but people just don't want to do it, for reasons already said that (market, and stuff). Rainbow Islands with 16m colors would be great, as would be Parasol Stars and many others games.
You can also design your own 2D games, and try to sell them
I am tryng to do a PC vertical shoot'em up, it will look like shit, but it will be fun to play (I hope). And I won't sell it, it will be a freeware game