It's just that Queen was never really that big outside the UK as far as I can tell. MJ OTOH, is still huge, here in China he's probably one of the 3 most popular recording artists, and the only one that's likely to still be popular 10 years from now.
Queen also mastered many different genres, had very clever songs, wrote ALL their own music, performed all their own music, did amazing LIVE shows which weren't doing with ropes & pulleys, etc. etc. etc.
As much as I respected MJ, he was more about the life style, the man, than about the music. He was popular because he was a wierdo and I can't help but wonder whether he'd be remembered so well if he didn't have such an odd life style.
Also if you want to see who is the best singer, listen to some demos of them both and realise Freddie's voice is far superior in general.
So yeah, Freddie Mercury all the way!
And no, Queen wasn't ever as big as Michael Jackson was in the US as far as I can tell, apart from some people that really knew Queen's music, you'd have a hard time getting most people in the US to come up with a longer lists of songs for Queen than for MJ. And I'm confident that remains the case even if you exclude the recordings that MJ put out after Freddie died.
And seriously, weirdo? That didn't come until after the main part of MJ's career was over. He'd had massive hits with both the Jackson 5 and on his own by that point. The really strange stuff didn't come until the early '90s. By the time the weird stuff came up his career was more or less moribund and the weirdness was doing far more harm than good as far as record sales go.