Invincible without hesitation and that despite being the album that took me the longest to warm up to- but once I did, man, it's good and I don't even mean tracks like You Rock my World. Some of the harmonies in Invincible are just smashing, the bridge in the Lost Children ("I see the door simply wide open"- that cello sound going up makes me weep on my knees) etc.
Thriller for me. I think it's a masterpiece and I like every song on the album. Thriller provides excellent songs such as Wanna Be Startin' Somethin', Beat It and Billie Jean, and right now You Rock My World is the only song from Invincible I can see being up to that standard of music.