This is the best sports game for the GBA that I have found.
To be honest, all I asked of the GBA was to please give me the original NES Tennis. I eventually bought an e-reader for that.
But Sega beat the e-reader to the punch and offered a GBA version of the greatest tennis game ever. Those of you privileged enough to own a Dreamcast know what I'm talking about.
This game has all of the elements that made Virtua Tennis so good. Those of you with XBOXes would see many similarities to Microsoft's Top Spin, because Top Spin completely rips Virtua Tennis off.
Career mode is the meat and/or potatoes of this game. and because you are playing a GBA game that didn't sell too many copies, it's probably the only mode you will concern yourself with. In career mode you train to improve your skills, enter tournaments to make money and raise your ranking, and buy new equipment to improve your play further. Sounds simple, but for a tennis game, this is an amazing amount of single player depth.
You have 4 buttons on the GBA, so the actual commands are simplified, but you can hit all the shots necessary (slice, drop, overhand, volley, lob) with ease.
The control is as fluid as any other modern tennis game. The training mini-games are diverse and FUN. When you complete career mode, there will not be much more challenge. 15-30 hours of highly addicting and enjoyable game play, however, is much more than satisfactory.