It's only natural (I guess) that MOST artist have a "peak" album. I guess the sad part is that once that album drops, there is no way an artist can ever repeat/exceed that performance (even if the future albums are technologically better) or can they?
I'll humbly list a few of my favorites:
Michael Jackson -- "Thriller" ("Dangerous" was a good follow-up, I thought)
Earth, Wind & Fire -- "All N All" (Many many great follow-ups!!)
Seal -- "Seal" (the second album, although the first was great too.)
Sade -- hmm...a tough one but I'll say "Promise" ("Love Deluxe" was awesome too)
Anita Baker -- "Rapture" (great follow ups too)
etc. etc. I'm sure this is something that NO artist wants to hear, especially those who've made it big, but this is just a microcosm of life, n'est pas?