I've been playing a few games lately on NES that I think would be awesome if they were remade into modern games. Blaster Master would make an awesome vehicular combat/first person shooter. Just imagine, maybe they could make multiple vehicles that you can get into and pilot, maybe a flying vehicle and an underwater vehicle or something. When you're in the tank, you could choose between a cockpit view or a third person behind-tank view, and when you're out of the vehicle it could be like a FPS with just you and your gun. It would probably be best as a PC game because of mouse/keyboard, but lots of FPS's have been coming out on consoles so they could port it to 360 or something, because it would have to have awesome graphics.
Maybe someone should make a UT2k4 mod like blaster master... I'm sure it could do everything I just described...
Another cool game I think would be the Legend of Kage. I don't know if it was a very popular game, but it was really cool because it was a side scroller with lots of freedom of movement and attack. The B button threw ninja stars in 8 directions depending on whatever direction you're holding on the d-pad, and the A button did a little katana strike that could block incoming ninja stars or kill guys at really close range. The first level of the game was the coolest because you could jump really high (you were a ninja after all) and climb onto trees, climb up trees, run along the branches, etc. You really felt like a ninja, you could go through the whoule first level without ever touching the ground because you could grab onto every tree trunk or branch, and the level is full of trees. I think that could make a really awesome new game, something similar to prince of persia or the new ninja gaiden (which I haven't played yet, but need to).