Sonic would always have the same formula: Sonic VS. Eggman (let's face it -- has Nintendo screwed up a single Mario game in the past few years?), Super Sonic playable all the time (after getting the Emeralds, of course), Sonic Boost, blah blah blah.
This sounds more like your wishlist for a Sonic game than if Nintendo were to buy Sega. I'd also like to say that Nintendo has indeed screwed up the Mario games recently by making them all exactly the same. New powerup, powerup is used all over the game to the point you're sick of it, end of Mario game. The stale formula is something I complained about a LOT back on Talk Nintendo, and I'll continue to do so here…I'd need to do more research to decide whether or not I feel it'd be a smart business move for Nintendo to buy Sega, but purely from your points, that's a wishlist for a new Sonic game, not a rationale for one company to buy another, particularly when there's nothing to indicate that Nintendo would do any of those things.
Nintendo should acquire them simply to diversify. Nintendo could probably do Sonic a little more justice than whatever Sega is dragging him through right now. Also, by acquiring Sega they get what is left of Atlus, which would give them exclusive rights to the Persona and Megami Tensei series. This would also diversify their portfolio by branching into PC gaming because they'd inherit Creative Assembly (Total War series) and Relic Entertainment (Company of Heroes and Dawn of War series). The Yakuza series would also become Nintendo's and that could be their answer for not getting any attention from Rockstar.
SEGA's doing fine with Sonic. I mean there's still good games with all the crap like Sonic Generations, Sonic 06... Okay those are probably the only good Sonic games that have come out lately and Sonic 06 isn't even recent, but hey it's a great game none-the-less. I mean Sonic Colors could've been better... and Sonic Lost World could've been better by not making it a sequel to Sonic Colors, and Sonic Boom wasn't that great because... we all know why, but it doesn't mean that the next thing they make will be bad. Besides Sonic Boom was made by some other company so even it's SEGA's fault for okaying it, it's not their complete doing.
If Nintendo buys out any company it should be CapCom or Konami since we know Konami won't last long.
A lot of the Japanese developers have fallen on hard times and Nintendo would be smart to scoop them up. Konami isn't in a hostile take over situation but they would probably sell their IPs if offered enough. Capcom is just blindfolded, wandering around in a dark room right now.
Nintendo buying popular third party IPs? That's not a bad idea. Nintendo buying Sega in particular? Well, I guess it could work. It just wouldn't be much more than an IP grab given how most of the original developers have likely left the company by now...
If anyone took over Sega, it should be Nintendo. Nintendo would be closer to fitting with the style of games Sega makes than anyone else. Well thats not totally true I guess, Sega can be pretty diverse.
It would be cool, though. Sega has so many cool things they never work on. Being under Nintendo, maybe we could see some of their franchises come back. Maybe even a sequel to Skies of Arcadia. Could be way cool : p
I thought Nintendo had already bought Sega. I know that Nintendo makes all of the Sonic games now. Wouldn't they have to have bought the Sega company to be able to do so?
Anyway, I'd be in favor of Nintendo acquiring Sega, they'd have access to a lot of valuable IPs. And let's not forget that, as benoit said, they would also own Atlus. It'd be disappointing to see the end of Sega as we know it... again, but I think it might be for the better.
