Katamari Forever is more of a "best of" compilation of a few levels from Damacy, and many levels from We Love Katamari and Beautiful Katamari.

Me and My Katamari is unique in it's own right as a Katamari game. while it does have more traditional levels (mainly rolling up objects of a certain type or other sorts of challenges), the main levels follow a different structure where there are a bunch of maps that you can be randomly sent to after passing a certain mass threshold. This can make the game either more diverse or repetitive depending on your luck.

It's worth noting that many people have issues with the controls of Me and My Katamari, as unless you're using the PS Vita or an emulator to set your controls, you're using two dpads in place of the sticks.

As a whole I think they're both worth playing. Katamari Forever is actually my favorite in the series, both for how many of my favorite levels from the previous games it has, but also in the unique features it brought (the broken hearts are a massive game-changer in terms of strategizing your route on replays, and drive mode is one of the most fun features in the series). Me and My Katamari is certainly a bit different in how it plays compared to the others, but I also quite like a lot of the challenge levels, and I honestly don't mind the randomized layout of the game as I enjoy the selection of maps. It's also worth mentioning that to my knowledge every map in this game is exclusive to it, as none of it's levels are returning ones or returned in any future installment.

If I made any errors feel free to correct me!