Honestly, I probably would've rated We Can Be Heroes lower if I had seen Sharkboy and Lavagirl. But, from what I've seen, there were only three major problems:
(P.S. Spoilers!!!)
-The Ending. The ending was so painfully anticlimactic that I sat on the couch wondering if it was some kind of joke. First, Grenada's good, then she's a bad takeover alien, then she's all good again. Same for Ojo. Finally, we realize that all the events about the alien takeover leading up to this point was pointless.
-The special effects. The alien tentacles were faker than my littles sister's Barbie dolls. They could've tried a little harder.
-Sound effects- Don't get me started.
Plus, as a bonus, Wild Card was super overpowered. He literally had every superpower you can imagine.
But, the message about teamwork was kind of nice.