I'm more familiar with the Soviet side of things but my understanding is:

• Mao and Stalin's leadership positions were kind of different towards the end of their rule. The Cultural Revolution is often interpreted as Mao trying to change the balance/structure of power, with Mao not technically in charge of the government, but influencing things as an ideologue if that makes sense. In comparison Stalin was pretty well in control the whole way. In more practical terms both Mao and Stalin were not quite as active in their later years, but I think Mao was in worse health which impacted on his presence in political terms and how he was presented in propaganda.

• This varied 'late period' would have meant a different environment for the successors. Stalin's succession was kind of sudden and involved a power struggle between Malenkov, Beria and Khrushchev. So Khrushchev had a good practical reason to attack elements of Stalin's legacy - his opponents could be presented as the darker parts of Stalin's legacy and hence attacked. Mao on the other hand, being in decline for longer, wasn't as sudden a transfer of power and there was less of a battle over his practical legacy.

• The Chinese Communist Party seems to have portrayed the excesses of the Cultural Revolution as the fault of the 'Gang of Four' rather than attribute blame to Mao. In passing I would note that neither Stalin nor Mao were attacked for their 'full' record, for example neither of them got much official flak for the famines that occurred while they were in power for example. In the Soviet Union blame, where attributed, was more so directed at Stalin and selected members of the Politburo (ie. Khrushchev's enemies). As to why the CCP opted to target the Gang of Four instead of also attacking Mao's own policies I would guess that was because Mao's public image was fairly important as a unifier. The Chinese may very well have taken note of the turmoil Destalinisation created for Khrushchev (eg. inadvertantly lifting the lid on dissent) and decided they didn't really want that.

It is also possible that the Gang of Four were weaker in practical terms than Beria/Malenkov/whoever Khrushchev was targetting. The arrest of the Gang of Four seems to have gone relatively smoothly and the CCP felt safe enough to put them through a show trial. The arrest of Beria on the other hand seems to have been presented as a bit stressful (though how much is hard to tell, Khrushchev in particular tended to exaggerate the story of his arrest) and Beria was dealt with rather promptly, again suggesting a fear he would be dangerous (perhaps symbolically if not in practical terms) if not disposed of quickly. So perhaps in the Chinese context the Gang of Four made for an easier and more convenient target, and attacking them rather than Mao was the path of least resistance.

I can think of two reasons:

One, Mao is different from Stalin in the regard that the former is widely seen to have founded new China, i.e. China after the Communist Party took power; whereas while the latter did lead the USSR to victory during WW2, he just doesn't enjoy the level of prestige as having founded a country. So, I suppose that that made it less costly to embark on destalinisation as opposed to any hypothetical campaign to historically indict Mao.

Two, unlike Russia which underwent the traumatic experience of having the USSR disintegrate around them, the Communist Party remains in power in China today. Despite the fact that much of China's economy currently runs on the capitalism, the ruling ideology of the country nominally remains communism. Seeing as that Mao is widely perceived in China as both a great political leader, in the sense of leading the CCP and therefore leading China by extension, as well as the source for China's ruling ideology - which is really not so much communism as it is Maoism, the objective features of modern-day China's existence, i.e. CCP still in power and communism as the ruling ideology, continue to inform and shape the perceptions of many - if not, most - Chinese of Mao as a great man.

It's true Mao isn't despised like Stalin, but I'm not sure "revere" is quite the right word either.

I taught a modern Chinese history class that had a lot of Chinese exchange students in it once (this was at an American west coast university), and though they toed the party line about a number of issues, not a single one of them was totally uncritical toward Mao. The general attitude seemed to be that while a lot of what Mao did was necessary for China's growth, and therefore on the whole it's a good thing he existed, he also did some really disastrous stuff - mostly the Cultural Revolution and the Great Leap Forward. One student actually came to my office hours to settle a debate she was having with her boyfriend back in China that pretty much came down to "Was Mao a heroic reformer who went too far sometimes, or a scheming megalomaniac?"