The consensus on the History forum is Makarov was a better and more accomplished hockey player than Kharlamov. This is based largely (but not entirely) on Makarov consistently doing better than Kharlamov in the scoring race and MVP voting in the Soviet leagues. (There's more to it than that, but that's certainly a strong starting point).
Why do most fans rate Kharlamov higher than Makarov? I think there are three main reasons:
Untimely death. Let's be clear. Kharlamov's death, at age 33, was a tragedy. But there's often a tendency to overrate players (or musicians) who died young. We won't know with certainty what else he could have accomplished but, like most Soviet stars of his era, he was already starting to decline by his early 30's (he was only 9th in scoring on his own team in his last full season).
Playing style. Kharlamov was a spectacularly talented, creative player. He was an excellent skater and stickhandler, and was very entertaining to watch. It's not uncommon for players like this to get overrated. (Gilbert Perreault was a similar player, and The Hockey News ranked him 47th all-time in their 1998 list of the hundred best players, which was an absurd ranking at the time. I'd argue that Pavel Bure gets overrated for the same reasons).
Perception. Most people in North America didn't see Makarov play until he joined the NHL in 1990, at age 31, when he was at the tail end of his prime. Kharlamov played in the 1972 Summit Series and was arguably the best player on either side through the first five games. In game six, Bobby Clarke slashed his ankle, which caused him to miss the rest of that game, all of game seven, and then he was obviously weakened in game eight. Kharlamov was stellar in the Summit Series, but five games in one tournament shouldn't override all of the other information we have.
Kharlamov was a great player. That's not in dispute. But I think he's clearly not as accomplished as Makarov, despite being more famous in North America, for the reasons listed above.
(I'll write something about Slava Fetisov later if I have time. As of now, he's only 8th on this list, which is far too low. Not that the History forum's Top 100 list is perfect - and full disclosure, I was a participant - but he was ranked the 2nd greatest Soviet player all-time, and 8th all-time among defensemen, ahead of some big names like Paul Coffey, Chris Chelios, and even Larry Robinson).