For the sake of not being long winded.

Everything by Capcom
Everything by Konami
Everything by Sunsoft
Everything by Nintendo

Sorry for being repetitive

Duck Tales
Mega Man 2
Final Fantasy (sentimental)
Bucky O'Hare
Super Mario Bros. (Trite, yes, but classic)

Both Zeldas
SMB 2 and 3
Monopoly
Deja Vu
Punch Out

Ninga Gaiden 1, 2 & 3
Mega Man 4
Zelda 1
Mega Man 3
1943
Mega Man 2
Final Fantasy

in that order

Duck Tales - Probably has my favorite video game music for any game. I remember enjoying it as kid too so it instantly triggers nostalgia.
Contra - Same as above. Heavy in the nostalgic area.
Mega Man 2 - Sure I rented it a few times as kid but didn't own it until a few years ago. So little to no nostalgic connections but I guess that's evidence of a fantastic sound track.
Castlevania - Never played this as a kid. Heard it for the first time in 2008. The theme from Stage 1 has those classic NES sounds. Even though I hadn't heard it prior to 2008 those classic sounds made it feel like I had heard it before. http://www.youtube.com/watch?v=JYfgpodCVHE

SMB2. I'm sure someone with higher knowledge on the subject will slam me on this one because I don't know if it's the exact same music from Doki Doki Panic. But the overworld theme is rather catchy and I always loved pausing it and just hearing the bassline. The character select music is classic as well.

Just wanted to add a couple,

Batman
Batman: Return of the Joker
Battletoads
Crystalis
Friday the 13th
Maniac Mansion

Many more of course just a few that came to mind that haven't been mentioned yet.

i gota say, those are 2 good ones that i initially overlooked. i have since come to appreciate the SMB3 music much more, likewise with punchout - though mainly a cover version of punchout. i'll have to go back and listen to the original punchout score sometime.

Gimmick! Seriously guys. Gimmick is the shit.

I am a huge fan of Sunsoft soundtracks...

I think my top 5 are:

1. Journey to Silius
2. Master Blaster
3. Super Mario Bros. 3
4. Mega Man 2
5. Zelda 2