A couple of thoughts:

1. People like more of the same if it was done well to begin with: you don't hear too many people complaining that another God of War is coming with, essentially, the same gameplay, do you? Devil May Cry? Zelda? Even games that seemingly get installments constantly (like, say, Ratchet & Clank) aren't looked on as being stale as they are typically well-done even if they have remained, essentially, unchanged since inception. Hell, look at how opinion is still split on Super Mario Sunshine--that was hardly anything like the defree of change made in Banjo.

2.  As Squrriel noted, it isn't like there's been many outings for Banjo at all. This is only the third game ever in the series and a lot of people were really looking forward to 'more of the same' (again, more of the same is good if it was done well in the first place). For Rare to turn around and say well, nah, we're going to re-invent the wheel, people are rightfully going to be skeptical.

3. Change can be scary/uncomfortable/unpleasant: how do you think fans of God of War would react if SCEA decided to make it a charriot racing game instead of a beat 'em up? Don't you think the fanbase would be threatening to burn down the gates of SCEA Santa Monica and staking out the corpses of the producer and lead designer before the gates as a warning to others? Even if it ends up being the greatest charriot racing game ever there is going to be a tremendous amount of resistance to the idea until people play it and, even then it might not get a fair shake because nobody was tired of more of the same just yet. If you can't relate to the God of War example, simply insert your favorite platforming game then take away at least half of what made that game that game, mix in something from completely out of left field, and think how you'd feel about it. Sure, you might be interested but, if you're honest, you're going to be at least somewhat skeptical of how it's going to turn out since there's really nothing like it to compare it to...

4. As near as I can tell, Rare has implied that this is the true sequel to Banjo-Tooie which is only going to make things worse since that means there isn't going to be a 'real' one coming any time soon (or ever). Think about if God of War was only going to be charriot racing games for the forseeable future--not only would those fans have raped and pillaged SCEA Santa Monica, but they'd have likely razed the entire city and LA to boot (which, speaking as a former resident, might not be such a terrible thing).

5. Rare's record has, at best, been mixed since the end of their run on GameCube. Outside of the universally-praised Viva Pinata, all of their intervening games have been received with very mixed reviews and receptions. Naturally this track record is going to be used to judge them (fairly or not) until they demonstrate that they can re-bottle the lightning that was once taken for granted.

Now, none of this is to say that a knee-jerk, ultra-cynical, reaction is always a good thing, but it also isn't such a good thing to be so open-minded to change and hope that your brain falls out. As far as a lot of people are concerned, Rare is going to have to earn their fans on this one as trading on the Banjo name isn't exactly making anyone particularly happy at this point.

 i checked ur games collection and i found that u are a BIG sonyfan so its hard to believe u ..... and stop trolling.

All I know is when Banjo blew up Mario's head in the trailer, I fucking lol'd.

Another good example of this is Final Fantasy XII which made the battle system more fast-paced and the story more political

 Ummmm....Jet Force Jemini?

What the fuck was that game all about

I was dissapointed because it is not the same anymore really really dissapointed but that doesn't mean it will be a bad game. It is like that Castlevania fighter..Fans are really dissapointed and already hate it before they played it;...Can still be good..

 happy now guys ??!! man ... cant survive from the fans !

Oh yeah Rare also made Kameo that was a very good platformer it was just to short but for a launch game you really can't ask to much.

(I hope Rare will make a sequel of Kameo their must be one).

Why do you constantly bring up Final Fantasy XII?

Final Fantasy XII did represent a change in the series and in the battle system, but the change was far less drastic than what they did to Banjo-Kazooie and only a moderately larger change than most series see between games. Its one thing to change the gameplay mechanic, its another to change the genre entirely ... What Rare has done would be similar to Square announcing that Final Fantasy XIII would now be a fighting game.

 You have gone too far my friend, do not hate on rare, you hear me!!!!!!!

(bulging vein in neck)

I expect this game to be great ;)