I prefer the Mario & Luigi Saga. Absolutely loved the last one (bowser's inside story!) Just the dynamic between characters and the brothers especially are great. It always has a funny witty little story. Paper mario has that as well, but I felt it was lacking something compared to superstar saga.
I also think the superstar saga is better than almost all the mario games (that's right even Galaxy). I feel that this saga is not generic and very unique and special. (special mention of the babies, they are also adorable inn Partner's in Time).
PSN ID: clemens-nl