Playing a monster, saving other monsters, beating up bad monsters... what more could you want!
Now running about on the map can get a bit old, if you've played Zelda or any of the Secret of Mana games you'll get an idea of what its like. Where this game realy shines is in the giant Tanks. The fact that you get to run around inside your tank, board your foes and smash it up form the inside realy adds a lot of depth to the game. I think other developers should look at this game and see how fun Large tank/ship/vehicle battles can be if you just add the extra layer of an interior.
Overall if your looking for a fun, solid game on your DS, somthing to keep you busy on the plane/train/boat or other than Rocket Slime may be just for you. With well done graphics, solid gameplay, and an inovative experiance Rocket Slime will keep you busy for a while (as long as any DS game realy could). Add a friend and the game gains a whole new demension as you fight eachother in massive tank battles. Seriously give it a try, even if you just rent it.