Katamari Forever gives more of the great Katamari experience, but it doesn't improve very meaningfully.
For those who have never played Katamari, this is probably the best place to start if you're worried about backwards compatibility or graphics, though due to the series' focus on artistic merit rather than graphical power, Katamari Damacy probably serves as a better representative, and is cheaper. The game's basic premise is this. The King of All Cosmos (for lack of a better word, God), accidentally destroys all the stars and gets amnesia. Now you, his son, The Prince, must roll up mundane objects in an ever growing ball called a Katamari. Virtually everything in the world can be rolled up, with the stipulation that you have to be substantially larger than what you pick up. This means that you can't just jump straight to picking up continents, you have to start small. And the game does start small, having you roll up pins and erasers, but ramping up the scale until stars and black holes are rolled in a single dash. It's an incredibly addicting system that rewards patience and planning, while still retaining a child-like and fun atmosphere.
Sadly, the game's multiplayer is the most lackluster portion of the game. Rather than opening up the game's beautiful environments to be played in by both characters, the multiplayer confines the action to a few confined maps with predefined challenges. For a game that is so addicting on its own, and has such amazing multiplayer potential, Katamari Forever gives a solid disappointment in this section.
In short, Katamari Forever is a decent Katamari game, but does little to add to the series, and needs a major overhaul to its multiplayer.