Pokemon - Yellow Version (USA, Europe) ROM

Pokemon Yellow is essentially Red/Blue with a bit of content from the popular anime series.
Red (or whatever you called him) is saved by Professor Oak and given a Pokemon to start his Pokemon journey. If you remember from the previous two games, you get a choice from 3 Pokemon laid out before you... not any more. Now, the only Pokemon left is the wild Pikachu that attacked you (and an Eevee, but Blue [or whatever you called him] takes that from you).
As you progress through the game, you'll notice subtle differences from the previous two titles, but it's basically the same with a splash of color added and some new sprites/Pokemon locations.
You may be thinking "But I wanted *insert Kanto starter here*! Why can't I get it in this game?". Though you don't get the 3 starters in Pallet Town, you can get them, all 3 of them. They are out in the world, and are given to you by different NPCs upon talking to them with the proper story requirements met. Now your team can rival anyone's.
This is still a first generation Pokemon game, but the story is different that owning this and either Red or Blue is justifiable. And it's still a fun game with nearly no downsides (I can't think of any off hand) so it gets a good rating from me.

This was the first gameboy color game that I owned, and the first in the pokemon color series, I was definitely impressed and addicted!
Although now, the yellow version doesn't match up to the newer versions, during the time of its release, the graphics and gameplay were really top notch. 
 

Like all of the pokemon games, you play as a trainer and your object is to train pokemon and collect badges. You also have to battle other trainers along your quest.
This game is great fun, even for those that aren't pokemon fans. It's sort of like an RPG, but not.

Pokemon Yellow was the third pokemon game (not counting the japanese Green version) to be released on gameboy/gameboy color. It was mostly similar to red and blue, but it featured colors, and lots of references to the pokemon anime.
The first thing you'll notice if you've played blue or red, is that you can only get pikachu as a starting pokemon. Moreover, that pikachu will travel outside of his/her pokeball, and follow you around, just like in the anime. 
This simple change has a somewhat big impact on the begining of the game, since the first gym is rock type pokemon. And rock type are immune to electricity... So don't expect to win this one with pikachu...
The only efficient method of beating Brock I've found is raising a butterfree, from either a caterpie or a metapod. Butterfree learns confusion, which is probably the only pokemon move available to you you, this early in the game, that can hurt reasonably well rock pokemons.
However, after the harsh begining, the game rewards you ! In Cerulean city and Vermillion, you can obtain the 3 starter pokemons, charmander, bulbasur, and squirtle !
Another thing to note, is the appearance of Jessie and James, the two inept team rocket grunts, along with their signature pokemons and meowth. They aren't much of a challenge though.
All in all, pokemon yellow is an interesting game for those who have already played blue or red before, but newbies might find the initial difficulty to be somewhat a turn off.