The Wonderful End of the World is a essentially a Katamari Damacy imitator for the casual PC market. Instead of being a tarball, you're a biped, walking with the arrow keys and optionally turning with the mouse, and as in Katamari, things you walk into adhere to you, increasing your size and ultimately allowing you to pick up larger things.
As befits something sold into the casual market, it's a lot easier; you get a letter grade at the end of each level, and anything over a B (which isn't hard to get) opens up new levels; no humiliating chastisement from the King. The UI isn't as physically satisfying as the dual-joystick controls of Katamari, but then, PCs don't have dual joysticks, and it's workable. The fact that it's easier isn't all bad, either; its a game you can pick up and play for a few minutes of goofball enjoyment, without having to endure the tenseness of Katamari's countdown.
The musical score is excellent, peppy, REM-like rock, the graphics clean and brightly lit, and the levels are well conceived. You're not going to throw away your Katamari discs, but World is an interesting variation and a nice change of pace -- and of course you can play it on your PC.
"imitator"
Imitator is a very diplomatic way of putting it. Katamari is really unique game, and this is a cheap rip-off. Sorry, Dejobaan.
"Rip off"
So... Is Age of Empires a ripoff of Dune II? Is Unreal Tournament a ripoff of Quake? Is Neverwinter Nights a ripoff of Ultima? Is WoW a ripoff of Everquest (or possibly MUD)? Novel gameplay dynamics are adopted and extended by others. That's a fundament of game history, from its earliest inception.
I played it. I enjoyed it. So I wrote about it.
Rip off
It is a clone, since the dynamics are not expanded, just recycled in a way that does nothing with them on it's own accord. So, to answer your question, AoE is not a ripoff of Dune II, UT is not a ripoff of Quake, NWN is a different game than Ultima, but Titan Quest, per instance, most certainly is a complete rip-off (clone, if you will) of Diablo II, as is a ton of other games of the ARPG "genre".
The case is the same with The Wonderful End of the World, which merely builds new levels around Katamari's original mechanic.
Mind you, it's a good cheap rip-off and I love what it's saying with that wide grin on its face.
Not quite a ripoff
TWEotW adds some stuff, namely the abstract levels where you're picking up words or pixels of vibeo games. It also changes some stuff, like the control scheme. It has a very different feel than Katamari, too: less psychedelic and more chill.
Shall we say that if Katamari is Diablo I/II, TWEotW is a tiny Dungeon Siege?
Genre
Katamari doesn't qualify as a genre. It's too specific.
You can say that there are a million things that make an RTS game, so AoE is nearly completely different from C&C (and it is). But Katamari Damacy and Wonderful End Of The World are as different from each other as this Chinese statue is to Micky Mouse.
I really don't understand why they wasted all that programming talent on a completely unoriginal idea. It's almost unethical for a company who wants to go the indy route. They have proven they can do better, too, so this really sticks out negatively.
I just don't understand their motivation. It doesn't quite look like a cash-cow either.
Genre, Redux
As Dan Scherlis says, "Genre is what we call one hit game and its imitators." Dune II, the ur-RTS, was as startlingly original in its day as Katamari is today. I suspect that Katamari is too odd-ball to serve as the fount for a genre of games with similar play, but it's not impossible; thus, I reject the argument that World is in some sense illegitimate.
I agree with Greg on this
I agree with Greg on this one. This game is a deviation on the Katamari model with some tweaks. That's progress, right? Even if this game is a "knockoff" as some write it off as, it helps define what Katamari isnt- which is how genres begin. There is potential for it. What about a positive negative mechanic that shrank your ball instead of enlarging it? Or a simple aesthetic change? And so forth.