1) Improve how damage is taken. Dying is ridiculy easy.
2) Maybe add a weapon (to go through walls, sometimes you just bash through one and break the building)
3) Dont make buildings go down fast. Make them bigger.
4) Make buildings still. THEN anymovement the character makes makes it vibrate more and more.
6) Make them like a maze. If i go this way, then i can pick this guy. BUT, if i do so it will be more difficult to go up and grab this other one. Make me try different paths.
Solve those six points (and what some more people below said) Add some nitrome-like graphics, and you get one of the best games the front page has seen (seriously, i dont understand how this idea isn't over-used)