I had n64 but never owned SM64... but I had OOT. Bought it same month it was released(didn't had an internet connection at that time- so you can say it was the same as buying a game on first day now).

How did it felt playing Zelda 64?
I just point three things:
- Freedom of movement. I could go whenever and wherever I wanted.
- stunning visuals. If I wanted to take a brake from my adventure I just set the view on sky and watched as moon/sun/clouds passed by... pure awesomeness.
- sound - simple, tough I liked it very much

... o, and maybe one more thing.
Legend of Zelda: Ocarina of Time is by far, the only game which I "visited" at night, in my dreams. As I remember it took me a lot of time, until I stopped thinking about Hyrule.

heh... when I buy a Wii, its definitely going to be my first Wii points purchase

I played DK 64 be4, so yeah mario 64 wasnt that much for me.
But OoT was just plain amazing

first time playing Mario 64, was awesome, Seeing mario run around 3d amazed me but controlling him run around 3d was even more amazing, I never put the game down when I first got it

Previously we only had a SNES and gameboys. When we got our N64 with Mario64, OoT and GoldenEye... OMG. Can't describe.

And yea, pulling and stretching Mario's face in 3D was awesome.

Stof nailed this one.

I think that we're talking more about what the leap that gaming made with these games felt like than about what playing them for their own sake felt like. I don't know that people who didn't spend a few years on older systems can really relate.

The jump to 3D with Mario 64 was amazing, but things didn't get really emotional until Ocarina. With Mario, I was impressed by what it was doing technically, and I was amazed at what I was able to do, but it wasn't a world. I was free, but I was only free within the limits of the game.

Ocarina really created the sense of a game world for the first time. It was fantastic at the beginning, but it felt like Mario 64. But when you see Hyrule field for the first time, you really do feel like there's nothing that isn't out there. I don't know that there's really a word for it. You feel free to explore limitless possibilities.

It makes me very sad on occasion that that feeling has all but disappeared now.

Super Mario 64 was absolutly an eye opener, the perfect WOW game. Ocarina of Time is the game that got me into Zelda, and I havent left yet.

I first played SM64 on DS and I felt 'yeah this i good' but I didn't think there was anything spceial about. It wasn't down to the controls eitehr cause I was quite impressed by them. Then again I do think Super Mario Sunshine is better than SMB3

It felt awesome.

But seriously, great choice of games to ask this question. Super Mario 64 and Ocarina of Time were probably the games that most "wowed" me. As stof before mentioned, I experienced total freedom in these games. Wow, just wow.

Super Mario 64 kind of sucks anno 2008, but Ocarina of Time still holds up well today.

Yes exactly. There's no other way to describe it. And I think it's impossible for people who are a little younger and grew up playing 3D games to really understand what it felt like. To walk around in 3 dimensions. I too remember playing SM64 just to run and jump around outside the castle. Of course, in the beginning, everyone sucked at the controls, it was the first time people were using control sticks like that, controlling Mario was therefore hilariously difficult. :p I remember freaking out whenever a bob-omb caught sight of me and came running towards Mario, I really had to scramble to get away from it before it exploded. :p It all looked so amazingly awsome too. Looking back, the graphics are terrible, but back then, ahh, no words. Just plain beautiful. No game will ever ever EVER be as new, as fresh, as special and influential as Super Mario 64. Completing that game was one of the best things ever.. I think I almost cried. :p 

And don't get me started on OOT. Ah, Hyrule Field. I remember not getting past the Deku Tree until a few weeks after I got the game, because I couldn't beat it. :p That was before I discovered Z-targeting. One of the greatest inventions in videogames ever, btw. Hyrule Field. Soooooooooo large. After OOT, whenever my friends and me talked about the size of levels in videogames, Hyrule Field was the standard against which everything else was measured. I had so incredibly much fun with that game, I used to just walk around the towns and fields and everything, talking to people, shooting things, smashing pots, hacking grass, swimming. Ahh the memories. *.* Kokiri Forest, Death Mountain, Goron City, Zora's Domain, Hyrule Castle, Lon Lon Ranch, Gerudo Valley, the Haunted Wasteland, the Desert Colossus, Kakariko Village, the Lost Woods, all the temples. Man, just remembering all this makes me wanna go back and play right now! 

Damn, it's utterly impossible to put into words the feelings and emotions I experienced playing these games for the first time. To me, they will always be the greatest games ever made.  

it was a feeling of having an orgasm followed by becoming incontenant with joy.... what do they call it?....... yeah thats right i had a joygasm! (with both)