If you love Starcraft, you'll like Lego Battles
You have only one resource - legos I guess. You can acquire them through chopping trees, setting up mines, etc. You build buildings and collect legos, amass an army, and systematically attack the outposts or bases of your enemy, defeat them, and move on. There are a number of species types, including pirates, olde english, aliens, and more. There is a light story with cutscenes to enjoy, and the game, overall, is quite enjoyable.
Completionists will relish collecting all 20 of the blue studs on each level, in addition to the chests and rare red lego blocks (which confer powers).
The game is surprisingly long, and offers replay value through wifi battles (correct me if I'm wrong on this - haven't tried it as I have no time for friends).
Most of all, the game makes me wonder why Nintendo wasn't able to land a more popular, system-defining game like C&C or other RTS game which could have put the little wonder on the map in an even bigger way. Yes, age of empires exists in a format on the DS, but it's not quite the same.
Total Annihilation: Kingdoms for DS, anyone?