Best sidescroller for GBA. Right up there with Gunstar.

User Rating: 8.9 | Metal Slug Advance GBA
This is one of the funnest sidescrolling series I have ever played. I watched my friend play Contra: the Alien Wars for SNES, and wanted to play a sidescroller afterwards, So I got Metal Slug. As said above, it's the best side-scrolling shooter I've played for a LONG while. There are two characters to play through the game with, they both control the exact same way. Tons of action and boss battles and weapon pick ups and cards to collect, which add to the replay value. I don't mean to compare Contra to Metal Slug, but Contra came off to me as more of a platformer than Metal Slug, in the way that in Contra you die if you touch an enemie, so you want to jump to different places to avoid them. With Metal Slug, you only need worry about projectiles and can concetrate more in getting in the enemie's face rather than avoid them.