It's really not. Most of Nintendo's franchises have seen significant changes as time goes on, such as the transition to 3D and some downright massive changes necessary to make that work. Super Mario Galaxy is a great example of them changing the formula pretty dramatically. SMG plays nothing like SM64, and I'm not just talking about the gravity gimmick. The level design and progression structure are dramatically different. Hell, Metroid went first person for its first 3D iteration. If that's not changing up the formula I don't know what is.
Pokemon, on the other hand, has always played it safe, staying extremely close to the original in every iteration. There are many incremental improvements, especially to the UI (the first gen UI is absolutely terrible), but the game itself as I described above hasn't changed an inch.
Sometimes I feel like I'm the only person who actually LIKES Pokemon as it is and really don't want them to change it. Sure, I'd like larger games (like HG/SS with all of the content it has), but at the end of the day I play Pokemon because of the formula it has. If it wasn't fun I wouldn't still be playing it.
Pokemon, on the other hand, has always played it safe, staying extremely close to the original in every iteration. There are many incremental improvements, especially to the UI (the first gen UI is absolutely terrible), but the game itself as I described above hasn't changed an inch.
Sometimes I feel like I'm the only person who actually LIKES Pokemon as it is and really don't want them to change it. Sure, I'd like larger games (like HG/SS with all of the content it has), but at the end of the day I play Pokemon because of the formula it has. If it wasn't fun I wouldn't still be playing it.