The winner of an Olympics event may not run as fast or throw as far as someone else has in another recent event. And the Olympics doesn’t necesssarily have the best competitors in the world facing each other in the final round, or at all. Never-the-less, the winner of the decathalon will be called the world’s greatest athlete no matter what other decathalon events have resulted in. Championships reflect a snapshot in time, so in any sport they may not convey much. We just know on one day someone was the winner. And they will certainly have the bragging rights until someone outdoes them no matter what term is used to describe them.
These are interesting questions, as in the Olympic tennis competition, most of the best tennis players in the world competed, which I’m sure cannot have been true of the basketball (because any NBA side could choose an all-American team that would soundly thrash most national teams - though no doubt that would be partly down to coaching and spending more time playing and training together).
I’m pretty sure the answer to the first question is a resounding “yes” - it’s the only major (I know it’s not “a major” as such) title he hasn’t won, it’s still an Olympic gold medal, and he is unlikely to get another shot (and if he does the tournament will not be on grass, relatively speaking his best surface).
The answer to the second question is a closer decision, and of course really depends on how Murray himself feels (as does the first in respect of how Federer feels). Some people feel they have achieved more at the Olympics than in individual tournaments because they are really representing their country at the Olympics, not “just” playing for themselves. But I suspect your implication is right; Murray would trade his Olympic gold for a Wimbledon title.
After all, Wimbledon is harder to win (the draw is much deeper so you need to win more matches), and they are all best of 5 rather than 3. This makes it a more testing event than the Olympics. Which is why tennis shouldn’t be in the Olympics; likewise football.
If I had to guess, I’d say that they’d trade if they could. Murray would rather have a Wimbledon title, and Federer would rather have a gold than this last Wimbledon title.