If I'm not mistakin', the first Pokemon game that I had was Pokemon Crystal. Yeah... skipped both Gold & Silver. It turned out that Pokemon Crystal came with my Gameboy Color.
My first Pokemon game was Blue. I picked Squirtle the first time I played it, always had in that game. I remembered the first Pokemon I trained to Level 100, Blastoise, and my second, Jolteon, kicking butt in the Unknown Dungeon. I was kind of ticked when they renamed Unknown Dungeon as Cerulean Cave in FireRed and LeafGreen. Lost some of it's mystery... oh well.
My first were red and blue, i can't remember which i played first, but i started with the origonal
Wasn' the unknown dungeon always known as Cerulean cave, i thought it was, that's what it's called in my red/blue(they still work perfectly)
When I was a kid, and up to five minutes ago, I had it lodged into my brain that it was only called the Unknown Dungeon in the Red and Blue days. Wow, I just made myself sound old. Anyway, Unknown Dungeon is a much better sounding name, I think, and when I discovered it was called Cerulean Cave in FireRed and LeafGreen, an exclamation point appeared over my head. Not really, but you get it :).
It may be that you heard of Unknown Dungeon from a Japanese game- I think Cerulean Cave's called that in Japan? It sometimes IS called Unknown Dungeon, I have a board game that calls it that. :P You get the legendary birds and Mewtwo in it.
Edit- In the board game, I mean.
Blue, soon after it came out. Hilariously, the first time I played through Blue, I filled up what I could of the Pokédex without trading with anyone. Haven't done that since...
Pokemon Gold. 16 Badges in two days, oh my god.
In the end I had 251 (Forced to hack for Mew and Celebi though :() pokemon caught, over 150 hours logged and about half of my pokemon were level 100 (The first of which was a Feraligatr).
I even managed to have a lvl 100 Cubone, I didn't want to evolve it XD
I can't believe I lost the game though :(. I think I may rebuy it if I can find it XD