Some people aren't fans, but I love the more humourous tone of Portal 2. I think it really lets characters like GLaDOS and Wheatley shine, and it makes things like the trip through Aperture's and its crazier characters like Cave Johnson land. The gels and other new puzzle elements help to keep things fresh too! I might just be nostalgia blind but I can't think anything bad about Portal 2, it's just such a good game. One of the first I ever played on PC.