If you’re going to get MMBN, just get MMBN3 because they all play exactly the same, and the story’s not so great in any of them. Each of them just has new features and chips added, so you might as well get the most recent installment. 2 added style changes (special armor based on your fighting style) and 3 added a navi customizer.
Metroid Zero Mission is a cool remake of the original Metroid, but it gives it some abilities that weren’t in the original and adds about 15% more to the game in length.
Castlevania: Aria of Sorrow’s really cool. It’s the most similar of the 3 to SotN.
Fire Emblem’s a fun strategy game, too. But one of TD’s avatars was in it, so it loses some points.
Edit: Bokati pissed me off when I tried it. You have to be in direct sunlight for it to work, and nobody likes sitting outside in 90 degree weather while playing a game on a screen with glare.
Seriously, Dai’s right though, all the games have a sucky plot and the exact same mechanics. It’s almost exactly like Pokemon, Start with crappy chips > Defeat enemies > Get better chips > Kill occassional <strike>Gym</strike> Robot Master > Get better chips > Kill more shit. Where it comes into it’s own is the amount of stuff there is to do once you’ve finished the main task. It’s still very much a collect-'em-all mindset for playing you’ll need once you’ve completed it though. Be warned.
EDIT, oh, other games, okay.
Wait for Megaman Zero 3 if you haven’t played it already. Only series of Megaman so far to have a decent plot. Standard side-scrolling shooter/slasher, but a lot of fun.
I don’t play many GBA games, so that’s all I can think of right now. :\
It’s good old genuine fun, fully customizable, and you get to beat up Piro and Largo (figuratively).
Plus, it’s linkable with another player, and, it’s simple and addicting when you go 2-player. You’ll most likely never see completely what the game has to offer due to the reputation meter (which you can’t see, which’s one of my main bugs about the game), but all in all, it’s good clean fun.
Castlevania:Aria of Sorrow. It’s the best since Symphony of the Night.
Also Metroid Zero Mission fucking ROCKS. Its all the goodness that is Super Metroid mixed up with the original Metroid and thrown on a GBA.
Uh the remake of SMB 3 is really good too.
Thats about all the really good sidescrollers I can think of right this second, I might remember some more later.