This is assuming only graphics matter.

Sony could make an action/adventure puzzle game that is every bit as awesome as any Zelda games but Zelda games would continue to be awesome too.

The Zelda games last because they are generally just incredible games.  I challenge you to find even a Zelda game that is just decent besides the CD-I ones.

There's room for more than one game in people's collection. 

Wishful thinking on your part... It will never happen. Its Zelda and there won't ever be anything that can compare.

zelda is to RPG's what mario is to platformers..there might be just as engaging games.. or even better ones.. but nothing can ever dethrone them..

Zelda's not an RPG!

No chance, too many loyaly fans earned over the years. There is no way a new franchise could engender such loyalty. Plus if making a Zelda-like game that is actually better than Zelda was so easy why hasn't anyone tried yet?

Zelda is more than the sum of its parts. Trying to copy the parts wouldn't do anything.

Zelda is an action adventure game with some RPG's elemens.

PLEASE play Spirit Tracks the game is PERFECT 10/10 in everything.

and of course NO game can beat the ZELDA HYPE.

There can be and have been better games than Zelda, but the fact remains that it is a proven and established formula that has lasted 20+ years. For those that just pick up a Zelda game and another game, they could easily be swayed with the proper formula towards the other game. But for those who have loved the franchise since day 1, no matter how much "better" the game may be, it won't compare to Zelda.
Personally I didn't like the first Zelda ("gasp" ya ya i know, but it's preferance). I did like Adventures of Link alot, although I thought Princess of Scheherazade was a much better game. A Link to the past did alot in terms of gameplay and Ocarina of Time perfected it, making it a true masterpiece. I liked Majora's Mask alot, although a little more could have been done, it was a great game in its own right. Windwaker completely killed it for me, I barely got past the visuals ( sadly viewtiful joe did better cell shading in my opinion). The gameplay was ok, but better effects and visuals would have made certain actions feel more rewarding. Finally Twilight princess restored my faith in the series (was a breath of fresh air after WW), so if they were to keep the TP visuals with Ocarina gameplay and story style, I would be more than satisfied.
With all that being said, Level-5 and team ICO, given the proper resources and support, are capable of having their great games leave a mark just like Link has. Offtopic: Dark Cloud 1 and 2 left a huge mark in me, as well as SOTC and ICO.

I know! It's not an RPG!

And... you talking to me? About the Spirit Tracks bit? 'Cos I've already ordered the game, I should get it sometime this week, yay!

well not in the purest sense.. my bad..in any case.. its an awesome series..