I loved Portal 2. Absolutely loved it. I loved the characters, every single bloomin' one of them (also, I want to marry Stephen Merchant after that performance), I loved the humour (absolutely spot on), gameplay was brilliant, the tests were thought-provoking, I liked the new mechanics a lot, the diversity between testing and... other parts (I won't spoil here) and it surpassed every expectation I had.
But I also love Portal to bits, too. I love GLaDOS, I loved the chambers, I loved the song, ending battle and overall theme.
Therefore, I don't think I like one better than the other. I think they're both amazing and it's some of the best gaming time I've ever ploughed into a couple of games.