In general, I wouldn't say that Nintendo has "milked" the NSMB series, they came out years apart before these last two, and that was honestly poor planning on their part. NSMB2 should have been released for 3DS earlier, to spread them out more. But I do understand, they wanted and Mario game for Wii U launch, and I'm glad they did it. Otherwise, I wouldn't say they've "milked" the main Mario series at all. As for Mario in GENERAL, sure, I could see the argument for he and his co-characters getting overexposed. But then again, I guess that depends on whether or not you see it as all one big "Mario thing", or if you see franchises like Paper Mario, Mario & Luigi, the Mario Sports games, Mario Kart, etc., as separate entities or not. I do, but that's just me.
When it comes to a specific franchise, I would say Activision certainly milks the SHIT out of Call of Duty, though that's to be expected these days. Activision seems like they won't publish anything without being able to pop out a yearly release. They've done the same thing with Guitar Hero, Tony Hawk and even Spider-Man in the past.
I guess a general rule for me would be, that if a company tries to release a new installment more or less every single year in main series of anything, that would be "milking".







