Portal 2 is the most polished turd I have ever seen in my life.
Sure, the graphics are nice and shiny. But the puzzles are both frustrating and way more linear than that they have any right to be. And that might not have been such a bad thing if there weren't way too many fucking levels.
Portal 1? I can start a fresh game, do a whole run from start to finish, and it still has me begging for more. Doesn't even matter that I've had this game for a decade - it's just that good.
Portal 2? I did exactly *one* run, and that shit took me days to complete and I actually had to force myself not to bow out halfway through. The only thing that kept me going was that I wanted to see the ending for myself. I don't think I ever even bothered to play the game after that, either.
And Portal 2's writing felt like shitty fanfiction. They pretty much ignored how GLaDOS pieced herself back together in the ending of Portal 1, and every single character felt like a bad charicature of itself. Cave Johnson could have been a good idea, but he ended up being so ridulously over the top that he didn't even work as a joke anymore.
And those two Portal robots. I don't even remember their names. The fact that they didn't show up in the single player story (minus a throwaway cameo during the ending scene) was such a huge wasted opportunity.
Portal 2 was just disappointing. Which is all the worse because it could have been so much better even with the stuff that they did decide to put in.