Reynolds' first attempt at portraying Deadpool in X-Men Origins: Wolverine was disastrous. Fans hated his version of the character as much as the movie itself. That all seems like a distant memory now. His second try at filling the red spandex in Deadpool's own movie in 2016 was definitive. Wade Wilson is Ryan Reynolds as much as Christopher Reeve still absolutely embodies Superman.
Other superheroes have barely been improved upon by different actors - unless you count Michael Keaton's realignment of Bruce Wayne/Batman as he made the jump from tv to the cinema screen.
Since then I'd argue that the various actors taking over the role (Kilmer, Clooney, Bale, Affleck) have only portrayed minor variations on the standard set by Keaton, and have not displaced him in the public consciousness. Same goes for all the new Clark Kents.
And while I enjoy Mark Ruffalo's Dr Banner/Hulk, I suspect Bill Bixby owns that role forever; likewise Noomi Repace with Lisbeth Salander.
As for James Bond, Daniel Craig's muscular, mean Bond resuscitated the franchise from life support, but I think most people still hear Bond and think Connery.
Strangely enough, I'd say William Shatner's Captain James T. Kirk might be the next best contender. Frankly, you can thank Shatner for Star Trek's very existence. In 1966 the show was in big trouble, and it hadn't even aired yet: it just wasn't working with Jeffrey Hunter's bland Captain Pike. Then The Shat donned the gold shirt, bounded onto the bridge of the Enterprise, and the rest is history. Miraculously, Chris Pine's Kirk is pretty great too.