These albums all came out the same year as Train Of Thought:

Common, Like Water For Chocolate
Ghostface Killah, Supreme Clientele
OutKast, Stankonia
Slum Village, Fantastic Vol. 2

So to me, it's not even the best hip hop album that came out that year.

Understand that I like the album, but definitely not in the conversation of greatest of all time.
I've always thought the second half of the album (outside of Good Mourning and Love Language)
was average and I just had a tough time getting through it.