Moss was definitely immature at the end of his Oakland tenure and in that disaster NE / MIN / TEN season, but his lack of production with the Raiders is a little overblown. He put up 1005 yards and 8 TDs on a terrible (4-12) Raiders team his first year with Kerry Collins throwing to him. 2006 was a disaster all-around. Art Shell was the coach; he hadn't coached in more than five years and would never again afterwards. Aaron Brooks and Andrew Walter were the starting QBs; they started a combined one game ever again in the NFL. Walter had a 3 TD / 13 INT, completed 53.3% of his passes, and was sacked on 14.3% of his drop-backs but someone managed to win two games; Brooks (3 / 8, 57.3%, 11.9%) went 0-8.The GOAT conversation doesn't even have Randy Moss as a polite mention. He is, quite literally, 7,000 yards short of the GOAT, and to frame up what I perceive to be your blind spot a bit better, Moss was a Raider for two seasons, at ages 28 and 29. In those two seasons, he dogged it despite having a huge contract and racked up 1,558 receiving yards over both seasons. At age 39 Jerry Rice signed with the Raiders and in his first two seasons racked up 2,350 yards receiving in two seasons.
Moss is fun to watch on tv now, but unfortunately for many, his form of asshole cost his teams production. Owens' form was just goofy and annoyed teammates, but year in and year out he was an amazing receiver.
The striking thing about Moss' career is that he played with several different quarterbacks and virtually all of them had career seasons with him. Randall Cunningham had his best passing year in '98. Then Cunningham got hurt and Jeff George had his best year. Daunte Culpepper was great with Moss and his performance immediately went to shit - at age 28 - when Moss left. Brady broke basically every record with Moss. Matt Cassel had his best season with Moss. I think this key to the Moss argument - you can reasonably argue he played with worse quarterbacks (noting that he played only two years with Brady) than Owens - but made them look good.
Owens definitely gets the nod on longevity - Moss was done after his age-32 season, while Owens was still useful through all the way up through his age-37 season. It's worth noting that Moss was extremely durable; he played 13 games his final seasons in Minnesota and Oakland and a full 16 games every other season of his career.
(Sorry, I'm kind of cross-responded to some of your other notes - yeah, Rice is the best WR ever, no doubt)