One of the best platform shooters EVER!
What set Turrican aside from all the other platform games out there is the sheer size of the levels and the amount of exploration you can do. Everything is vividly detailed and it's full of eye candy. Plus the music it to it was some of the best ever heard on the C64. However I did find the Sega interpretation of this music to be somewhat dull and nowhere near as lively and upbeat.
It's also one of the very few games I managed to complete without cheating, I felt very proud when I was a kid but I must confess to using the Game Genie to finish the, much harder, Sega version.
You play a man in a suit of advanced armor (the Turrican suit) who must fight against loads of aliens and machines in order to save the earth. It looks a lot like Metroid for the NES in fact. And I'm kind of sad that although it spawned a few sequels, Turrican never really took off to be such a successful franchise like Metroid did. I really do think that a new Turrican game on a console such as the GBA or Nintendo DS would be a great idea. The game has such potential to work brilliantly as a new title on newer hardware.
Overall, it's a great game and it was released on so many old-school consoles that you must have come across it at some point. If so you'll know what I mean when I say it should be brought back.