Pokemon - Crystal Version (USA, Europe) ROM

It's the summer of 1998. The last thing you saw in the first episode was Ho-Oh. And before you knew it, Pokemon Gold and Silver were announced. They were released and were a huge hit! And then came Crystal.
This game was the first to feature animated Pokemon on a handheld device. It also improved most graphics such as remaking Entei and Raikou's sprites to match their artwork, and fixing most sprite related bugs. This game also introduced to option to play as a girl which would be featured in many games to come.
Overall this is a great game. I'd reccomend it to any pokemon fan. 
 

Pokemon Chrystal is a fantastic RPG for all ages as you embark as a trainer with dreams of becoming the best trainer in the world. This game is a classic and always will be!

Even though most of the Pokemon games had the same storyline for a while, I still like this game, I highly recommend it if you haven't played it... Definately 5/5

Travel back to the world of Johto as the Gold & Silver series continues with brand-new features! Whether you're reading the fresh descriptions in your Pokékdex, using the unique sort function to organize your Pokémon in new ways, watching the all-new battle animations, or discovering another way to capture Suicune, you'll need all of your Poké-skills to master Pokémon Crystal on your Game Boy Color!
 

This is without a doubt the best Pokemon version for the Gameboy color!
I came from playing the yellow version and I could not get over the difference. The gameplay is similar enough, but the graphics are far improved, not to mention this game is in the johto region, unlike pokemon yellow. 
Like all of the pokemon games, you play as a trainer and your object is to train pokemon and collect badges. This game is great fun, even for those that aren't pokemon fans. It's sort of like an RPG, but not.