The main problem CGI family-friendly flicks (produced by those other than Pixar) have, is that they aren't from Pixar. The gang that gave us such greats as Toy Story, Monsters Inc, and WALL.E really know what they're doing, and frankly everyone else is trailing in their dust (although Cars was a noticeable mis-step, and Ratatouille wasn't much better).
However, Dreamworks (who have given us the hugely successful Shrek films - none of which I've seen - and the two Madagascar movies - both of which I've seen and rather enjoyed) continues to do a stand-up job of walking in Pixar's shadow, while producing solid fare.
Monsters VS Aliens is such a film. It might be a little light on the laughs at times, and the plot can sometimes drag a little here and there (before feeling a bit rushed and undercooked in the third act), but the quality of the characters carries you through - especially the Seth Rogen voiced B.O.B, who steals every scene he wobbles through. Add in Keifer Sutherland's gravel-voiced W.R. Monger, Reese Witherspoon's cute-and-huge Ginormica, Will Arnett's cocky, Creature From The Black Lagoon-riffing The Missing Link, Hugh Laurie's mad, cock-roach-headed Dr Cockroach and a wide-eyed Insectosaurus, and you've got a good, fun movie.
It doesn't contain the same level of heart or originality that engenders Pixar's greatness (I'm really looking forward to checking out Up), but it's a really fun flick packed with references for sci-fi and monster movie lovers.