Yeah, you can have multiple rivals, but THE Rival always marks most mens careers. If you ask a majority of wrestling fans to say one name for Rival to the Rock, Austin will probably make that list 75% fo the time. Likewise with Bret Hart and Shawn Michaels, they exist together. Triple H has never had the great career rival like others have. Hogan has Piper, Flair and Sting, yadda yadda. Nothing springs to mind with Triple H as a great career rival.
But that's what makes HHH so good IMO.
He has been able to compete with everyone on the roster at any given time and make them look credible.
I know there are a lot of people who think HHH is a piece of crap when it comes to putting people over, but despite the outcome of a match, they're always reasonably entertaining.
A little over a year ago, he actually made the Great Khali look somewhat decent in the ring.
I don't think a guy needs a defined "rival" to make his career legendary.
The Rock is a legend for his mic skills, not his ring skills. Austin is a legend for the storyline he played out with McMahon. Foley is a legend for taking the sickest bumps the industry has ever seen. Sting is a legend for simply never signing with the WWE. Hogan is a legend for making the WWF / WWE popular. Flair is a legend for simply being Flair (and a 16 time world champ).
All of the aforementioned guys would be legends with or without a main rival based on everything they did for the industry, not just a certain person they had good matches with.
Does HHH have a legacy yet ?? No, he doesn't. But having a thousand matches with Orton isn't going to provide him with one. Becoming a 17 time world champ will and that's why he pushes himself down our throats (which I don't mind - I love the guy). But in all honesty, can you blame the guy for wanting to create a legacy for himself, regardless of how contrived or undeserving a member of the IWC deems it to be ??