I much rather have a Margaritta, frozen please. Thanks.
Fischer or Magnus?

Okay, then I'll bet $73.00 on Magnus Carlsen(I have to use the rest for something else). When do you send me the money to bet with?

Magnus FTW!
FTW?
For The Win! (although toasted waffles would be nice.)

Who would you put your money on if they were both playing at their peak?
Well, Carlsen seems to still be on the rise, but could be expected to outplay 1970s Fischer, having studied the latter's games, a lot else that has happened since then, and had the benefit of computer training.
Chess has evolved, and plucking Fischer out of the 70s would be unlikely to do him many favours, any more than Morphy is going to do anything other than be trounced by today's top players, despite his amazing record back in his own time.
Even Capablanca, having the highest computer match-up rate of any historical player up to present, would doubtlessly struggle against today's top players, given the advances that have been made in opening theory since then.

Well, of course. That is why Fischer invented Chess960! lol
But seriously, that is probably the only logical format we could use to compare players from different eras.

Who would you put your money on if they were both playing at their peak?
Well, Carlsen seems to still be on the rise, but could be expected to outplay 1970s Fischer, having studied the latter's games, a lot else that has happened since then, and had the benefit of computer training.
Chess has evolved, and plucking Fischer out of the 70s would be unlikely to do him many favours, any more than Morphy is going to do anything other than be trounced by today's top players, despite his amazing record back in his own time.
Even Capablanca, having the highest computer match-up rate of any historical player up to present, would doubtlessly struggle against today's top players, given the advances that have been made in opening theory since then.
I'm sure Fischer, and Morphy wouldlose if they were just plucked out of their time, and made to play today, but what if they had the benefit of today's training?

If both were playing at their best? Ah, the hypothetical match-ups and comparisons: nothing makes for a great argument like a proposition which is impossible to verify!
But from what we know, Carlsen would probably own Bobby. Fischer was great at exploiting weaknesses, Carlsen avoids creating them. Carlsen's strength is in creating and playing the very sort of even-but-not-sterile positions that Fischer found most taxing.
Good answer. :)
Who would you put your money on if they were both playing at their peak?