For almost as long as there have been video games, there have been ports that try to cram games onto hardware far less capable than that which it was originally designed for. Many of these were even considered impossible, only for a determined dev to come along and pull them off.

Which ports impressed you the most in terms of defying your expectations of what the target hardware could handle?

Turrican on the C64

Turrican on the SNES on a 4Mbit cartridge (500KB) to save money

Street Fighter Alpha 2 on the SNES, a cartridge game with loading times

Doom on the GBA

Rise of the Tomb Raider on Xbox 360 was quite an impressive port job, in my opinion. A standout at a time when last gen ports had to sacrifice a lot to run smoothly.

But, Turrican debuted on the C64 didn't it? Pretty good game. The music ( when they chose to actually play it ) was awesome.

Turrican  was developed on the C64  then ported ,so it was going to more capable devices rather than being ported to less capable ones

Yes  you beat me to it,  in my post below yours, I mentioned it was developed on the C64 and ported to more capable devices.

I never thought we would get GTA LCS/VCS on the PSP. A REAL 3D GTA game on a handheld? That was nuts at the time.

while I agree,it was a great bit of coding , this thread is really about ports to less capable systems  that exceeded our expectations of what could be done.

Street Fighter 2 on the Commodore 64.
https://youtu.be/lO_rJR7geT0?t=2m44s

Street Fighter II on the SNES, relatively speaking, was probably the biggest of those, on terms of technical achievement, resulting sales and the game's influence.