R.O.B. is, by far, the most versatile character in Brawl.
That being said, this prevent him from truly shining in any one aspect (except maybe recovery). That means it's up to the player to exploit R.O.B.'s strengths against the particular player and character he is facing and underpinning their own weaknesses rather than trying to rely on a particular exploit.
Hugs, I think, is an example of what a R.O.B. player should be. His "reactive" strategy is exactly how a R.O.B. should work; prevent the opponent from doing his thing by countering it with good strategy. R.O.B.'s versatility lets you do this in a number of ways, either allowing you to modify your entire strategy to counter the opponent's or to add something to your current strategy to keep something the opponent is doing from working.
In contrast, a character like Snake relies almost completely on stage control and overpowered KO moves, Metaknight relies on rushing and overwhelming the opponent with attacks, Ganondorf requires carefully gauging the opponent to find an opening and punish with a barrage of damage. R.O.B. can actually do all of these pretty effectively (except for the overpowered KO moves), but not quite as effectively as these characters can. He's a jack of all trades, so he'll be able to perform anything you want, just not to an uber level, kinda like Ivy from SCII.