A nice thing about the GBA to me is that despite it being over a dozen years old now the system was so well made that the quality that it could put out and did in various games still holds up very well today against your usual tablet and indie fare that often shows up. A nice perk Nintendo robbed us with once their handhelds went online was open region support.
Do you have any personal favorites or recommendations from outside where you live, or stuff that's so bad or unplayable (language or crappiness) that it's worth saying to avoid?
To start I'd throw out there that from the UK if you're a pinball fan I can think up 2 packages of games very worth grabbing, and they're cheap. Pinball Challenge Deluxe is a mix of the classic Amiga/DOS era games Pinball Dreams and Pinball Fantasies, each had 4 games so this one has 8. A fantastic blend from the best maker of digital pinball in that period of the first half of the 1990s. The only downer is that the game is built so save scores, the cheapo UbiSoft ditched the battery to save a buck so if you use it on an emulator or a flash cart you have scores to keep, a real game (like I have) will not. The other is much smaller with just a few tables but the designs are solid and that's Pinball Advance which may top out at 3 tables but they handle well and the ball works as it should, and it's definitely no boring or overly generic like a lot of other 'normal' style pinball titles on the system.
Another worth throwing out there but well known, from Japan - F-Zero Climax, the third we were denied and by leaps and bounds the best F-Zero experience on a handheld. The jump in quality with control, track design, audio and visuals are crazy good, a sprite level high detail game closer to the Gamecube than the SNES in style. A nice true gimme is the 64DD track editor makes a return on the cart and allows you to make and save up to 4 courses on there to play.