1. Super Mario 3 - Yeah predictable I know but it was just so big and so beautiful. In fact all three NES Mario games are my joint number 1.
2. Legend Of Zelda - This is my favourite Zelda game of them all! Such little dialogue and simple graphics, but so mysterious and enchanting. This one had me playing for months as a little kid. I got stuck quite a few times but could never give up. Admittedly I did consult a guide at one stage but I had no internet back then (early 90s) so I had to go to a bookshop and read it in there.
3. Snake Rattle and Roll - What could be better than 2 player simultaneous action featuring snakes eating coloured balls and climbing up a mountain? (or whatever it was) This one was almost 3d, well not really but the closest thing to 3d back then. It was quite confusing to do some of the jumps and absolutely ultra rock doom hard to finish it. I never did. Great 50s soundtrack.
4 - Fantastic Adventures Of Dizzy. This was like all the previous Dizzy games rolled into one with better graphics and awesome music. This really could have used a save game feature though because it was huge and would have taken weeks to finish (never did because I wasn't allowed to leave the NES on overnight). The cartridge didn't even look like a normal NES cartridge which scores it bonus points for non-conformity .
5. Maniac Mansion - First point and click adventure I ever played, only one I ever liked. Just thinking about this makes me feel all nostalgic. The music was amazing and the fact that you could get one character lost or stuck and just switch to another was great. I never came close to finishing it.
I'd like to mention that Metroid is probably better than all of these games but I only just thought of it. Tough shit. Honourable mentions go to Solstice, Double Dragon 2, Little Nemo, Dr. Mario, Chip n Dale, Tecmo World Wrestling, Street Gangs, Paperboy, A Boy and His Blob, MEgaman, Faxanadu and Kirby. Great days.