I think the first 6 are all very good albums. I went with Sabotage. It is probably my favorite all time album by any band. Sabbath experimented a bit more with that album and I think it turned out great. SBS, Vol 4 and Reality are classics too imo. I like the first two albums and although that is where alot of their more popular radio hits are from I don't think those albums are as good as Masters Of Reality thru Sabotage.
I thought it would be a good time to post this as a poll considering that Sabbath are due to release their new album sometime next year.
1-13 Philip H. Anselmo & The Illegals