Well, I liked the ending. But I think I wouldn´t like it if there wasn´t the manga. Because then it would be the ending of Gantz and that would suck. But for me the manga is the "true" Gantz series so I could enjoy seeing some new stuff without caring if the anime ending is a good ending for Gantz(because I still expect the ending). I found the anime kinda boring after reading the manga, so I was looking forward too see the new stuff. It kinda remembered me of Battle Royal with that "who´s playing" thing. Furthermore I asked myself how this situation would end. Quite intersting.