I'm gonna jump on the bandwagon and also post that the games range from 8 to 512 mb, just to up my post count.
Just kidding, on the contrary, here's a little something you should keep in mind, especially when it comes to the 512 mb fat games.
It's true that depending on the size of the chip of the cartridge you always have rom sizes with 2 power n (2 power 1 =2, 2² = 4 etc.)
but the real romsizes when looking on the actual code of the game are rarely the full size of that.
So when you have a game which actual size is actually 9 mb, you are forced to take the 16 mb sized chips so the whole game can be stored, 8 is obviously not enough. The wasted space then will be just filled up with garbage.
Of course this is true with all games, but the bigger the size the more likely they tend to have more wasted space because the actual size of the game is smaller but you just went a tad over the 256 mb mark and don't want to scratch anything out so you grab the 512 mb ones.
On a side info, that's what rom trimming does if I am not mistaken, it cuts the wasted space away that got along with dumping the full rom chip.
This aint gonna change anything to the thread openers original question, but I just felt like adding information.
So even when you hold an impressive 512 mb sized rom in your virtual hands, its quite possible that not all of the mb is playable fun.
But this is just a natural progression that went on when developers started to dish out games with lots of content, but I doubt there will be normal DS games that will break the 512 mb mark, DSi games would make this more likely and 3DS games definitely are bigger than that.