Which Developers Are Best At Improving Their Games?

With the Insomniac thread as well as my almost-complete playthrough of Digital Devil Saga 2 (after finishing DDS1 a month or so ago), I started thinking about games that were much better than their predecessors...and some games that weren't.

Doesn't seem like a big deal. You have a great game, so it shouldn't be hard to make it better. Tweak some things, improve the graphics, put in more maps, increase player count, etc. But it seems like it isn't quite so easy to do. Some developers may end up implementing too many "improvements", and the game ends up missing the elements that made the original so great. Other developers, on the other hand, seem to be pretty good at keeping the core of the game largely unchanged, but addressing the few weak points that were disliked by fans/critics.

As mentioned, DDS2 was a bit of an influence for this thread, so it should be no surprise that I'd mention Atlus (or specifically, the SMT team(s)). DDS2 was released ~6 months after the original, but was much better IMO (and I enjoyed DDS1). Might just be how they planned it, given the unique circumstances with the series (much more involved in DDS2, so easier to like it better). That said, I feel more or less the same about their other games as well, so not just restricted to DDS.