Great Replay Value.
I was interested with the new Samus, who lost her suit. Shortly after, at the end, she gains it back, and kicks even more butt. I am even debating whether I like her blue armor better or not.
Her weapons are badder than ever. With Ice missles, spread shot, Gravity gear, Screw ball, Super Power Bombs, it all gets better. I had fun wiping everyone out with them.
Also, the addition of the SA-X was pretty sweet. fighting multiple clones of yourself was pretty cool. The graphics were pretty good for a GBA, and the gameplay was pretty good. The sound, however, tends to get boring, and might leave you putting some headphones on. An easy game, but very hard to get tired of. The Learning curve was easy, and I mastered the game it ten minutes.
The reason I am giving it such a high playing time is because I have beaten this game about ten times.