I don't think people are necessarily excited about the IP so much as they're excited about playing new games from a company that puts out some really great games. A lot of Nintendo fans would much rather Nintendo unleash their talent on some new IP, and games like NSMB 2 are getting a very skeptical reception even from Nintendo fans.
And really, besides Mario (and even then, 2D and 3D Mario games are quite different), they don't put out games in these series all that often. There have been 3 console Zelda games and 3 handheld Zelda games in the past decade, and about the same number of Metroid games. Compared to most other franchises, that's not really that bad.
I'm not going to try to claim that Nintendo doesn't get a bit of a free pass sometimes, but considering the (western) gaming press regularly shits on the Wii and can't stop talking about how Apple's going to kill their handheld systems, I'm not sure they're the golden boy you're saying they are.
I agree. Nintendo isn't putting out the same games every year. The closest thing they have is putting out a bunch of "new" SMB games recently, which they've totally been called out on. I mean there was what, 5 years between Twilight Princess and Skyward Sword? That's not an annualized franchise, and those games have some pretty significant differences, even if they both fit the Zelda mold.
It never made sense to me that you had to buy a copy of a game and then pay to keep playing it, so in my mind subscription fees were never really justifiable. Of course, the only MMO I ever really got into was Runescape, so maybe my opinion isn't really important. On that note though, a subscription fee makes more sense to me if the game doesn't cost anything up front. In that case, I'd prefer it over the free to play/micro-transactions model.