I'm probably a bit biased due to my everlasting love of classic Bionicle and the fact that I have 13, soon to be 14 copies of this game, 5 of them for DS, but it really is a solid game. The controls are nice, there's plenty of extras to unlock and powers to upgrade, and it has quite solid controls with several different options. Personally I prefer the buttons for looking around, but if you prefer using the stylus you can also do that,
It also has a good selection of levels with plenty of secrets to find to unlock the extras. Sure there's a spot where I fell through the ground a couple times, but no game's perfect. Also gotta mention the extras. From tiny enemies to a default weapon that shoots random farm animals or literally making every weapon sound into a person trying to imitate it, they're completely silly and lovely. And the feeling of completing it 100% never gets old, be it the first or eighth time.
Even just the little things like the music are quite good for a DS game. Maybe not super special on its own, but it adds a lot of character to the levels.
The enemy selection features pretty much all the baddies from the previous years, from Bohrok to Visorak, adding decent variation to the enemies, even if there can be a bit many of them now and again. But the game does have unlockable one-hit defeat, so that won't be a problem when replaying al lthe levels again to complete it.
While on levels, I personally love how you can start with whichever level you wish. Stage one of all six levels are available from the start, so whether you want to grab masks and power them up fully one at a time or just grab every mask and have a much more varied if weaker arsenal from the start is all up to you. Add to that the three more stages and boss fight per level and extra bonus levels after those and there's plenty to play in this gem of a DS game. Add to that the three save files per game and this game has more than plenty to offer. Overall it's just a great game for any DS collection.