As I have honestly never played Katamari Damacy I can not compare the two games, however, this is one of the finest games I have ever played. At first look you just think "What the heck is this?" but then you begin to play it and it is amazing. We Love Katamari combines fantastic rolling up gameplay with funky music that will be stuck in your head for weeks. The plot is unbelievably wierd (in a good sense) and the King of All Cosmos is hysterical. There are so many cousins to collect and things to unlock. The only flaw I currently see is the versus mode which is not very fun... although the co-op mode is fantastic. At first it is a little wierd to control the same Katamari with two people but it begins to become easier and you have a heck of a good time. Although you may believe you would get bored the levels are so diverse from one another and you will find yourself playing them over and over again to collect everything. I do wish it was made for the Gamecube as well as the PS2 though. It feels that this type of game should be for the Cube except for the fact the unique analog controls wouldnt work as well.
All in all this game is a must buy for the PS2 and may even be a reason to buy a PS2 (when it drops to the special $99.99 price).