I've still only touched a handful of the ten free Game Boy Advance games I got along with other early Nintendo 3DS owners late last year. I've played quite a bit of them though, and this is what I think.
F-Zero: Maximum Velocity - There's a type of gamer that has emerged fairly recently, one who probably has the skill to complete games on harder difficulties, but is more interested in seeing all the content a game has to see than being challenged, and so plays on easy mode in order to do so without frustration. They are content tourists, and I have been known to become one when I'm playing a type of game I'm not really into. Racing games where you have to finish a certain place or better to advance to the next course are not kind to this type of gamer. F-Zero is even worse, because there's no chance of coming from far behind - you have to finish at a certain place in each lap, and that place gets higher with each circuit. And with the fact that every course looks pretty much the same, I'm not much interested in acquiring the skill to do better in order to see all that content. A functional game but not a very fun one.
Mario Kart: Super Circuit - Super Circuit is a bit better than F-Zero, because at least the easiest mode actually seems like it's pretty easy. It's still not terribly entertaining, though - racing games done with non-3D tracks are just a dicey proposition, and this version of Mario Kart is playable but just not very enticing. I've played a bit of Mario Kart 7, and it's night and day how much more fun that game is, even with the increase in annoying item usage. Another game I don't intend to revisit.
Mario vs. Donkey Kong - This is a fun though occasionally frustrating puzzle platformer, which at times places great emphasis on both of those skills. Donkey Kong captures a bunch of Mario's little robot versions of himself, and he has to get them back. Each world has a similar progression - six standard levels, which require you to find a key on one screen and then a robot on the next, a seventh level where you have to guide the robots you've collected to a toy box, and a boss level where you face off with Donkey Kong before he runs away and you go to a new world with a different theme. As I said it's a pretty entertaining game, though there are some weird quirks, like how there's a tutorial video before each level that only hints at what you'll have to do next, and even with all of that help plenty of game elements are introduced without explanation. A whole second mode was unlocked after I saw the credits the first time, but I don't find myself interested in it - I think I got my fill of the gameplay already.
WarioWare, Inc.: Mega Microgame$! - I definitely had more fun with this than anything else on this list, despite the WarioWare thing not really being a fresh concept anymore. The game is basically the industry itself in a nutshell - you visit various developers around the city, and try out their various games in some sort of strange situation that can handily represent your metaprogress in the actual game itself. The games can mostly be finished in three seconds or left, and your goal is to just finish as many as you can before you make too many mistakes, as they are randomly chosen and fly by at great speed. It's a funny and addictive experience that's also packed with a lot of extras such as endless versions of some of the microgames or special two player ones which can be played on a single system. There's a manic, crazed energy to the whole thing, and it's just a good time.