On the topic of Rare ...
Back in the day (SNES and first half of the N64) Rare was an amazing developer that was full of highly talented creative individuals who could deliver a quality product on a reasonable timeline. Their success actually caused a lot of their problems though because these highly talented creative people were leaving to start their own companies (publishers were throwing money at senior Rare developers for start ups) or being attracted away from Rare by other studios. As this was happening Rare games were being constantly delayed and (it is rumoured) Nintendo became more and more involved with the inner workings of Rare to ensure quality was still maintained.
By the time the Stamper Bros. offered to sell their share of Rare to Nintendo, Rare was a shell of the company they used to be and was not worth what the Stamper Bros. were asking. Microsoft (to build credibility as a first party developer) bought Rare for top dollar from the Stamper Bros. and Nintendo, and Nintendo used that money to buy other studios (Retro) and to finance many Gamecube games.
After the sale of Rare, the management and culture changes within the company drove the remaining talent away from the company and all Microsoft was left with was a series of half-finished projects and IPs it didn't know what to do with.
In my opinion, the reason we don't see Rare going head to head with Nintendo in the platformer market is because Rare no longer has anyone in it that has experience producing quality platformer games; and it would take Microsoft years to build a team that was able to deliver a Banjo Kazooie game that was on par with a game like Super Mario Galaxy.
