I think it's too early to call for them being better than Rare.
Silicon Knights has only released one game under Nintendo thus far (previous games include Blood Omen, Steel Empires, and some other games... although I have only played Blood Omen, which was a great game although had horrendous load times), and although IMO is was great, I wouldn't call is a masterpiece (although I would call the storyline such).
Rare over the years has delivered the amazing classics that are Donkey Kong Country and Goldeneye, as well as other great games such as Conker's Bad Fur Day (although I didn't like the change in direction), Blast Corps, and Jet Force Gemini (hated the last part with the Tribals though... that just killed the game for me but at least the rest was great). Banjo-Kazooie was good too but the controls just didn't feel solid enough for me and the collecting still urks me. Star Fox Adventures was a mediocre game, but everyone makes a flaw in their track record (although they sure took a long time to pop out a mediocre game) and at times multiple. We'll see how things are down the line when Rare releases their X-Box line-up. I'm personally looking forward to Kameo and Conker, Banjo is good but nothing special to me while Perfect Dark Zero doesn't really raise an eyebrow from me, especially compared to many other quality FPS games that have been released and will be release... is those games in my mind live up to the hype of course).
However, I honestly do look forward to Too Human and Metal Gear Solid: The Twin Snakes than Rare's offerings, but that doesn't mean I'm going to downplay Rare just because they happened to have start out rough this generation. For all we know they may actually release a new masterpiece in the future. Not say their going to but you never know.