Leno has been up and down too. He went from below average to average and then slightly above last season. Credit to him, but not sure his body of work is "top 7" at all. He's a solid LT, but not elite.
You are right about Fuller, but he was actually pretty good his rookie season and then was terrible after the coaching change (namely because he didn't fit the scheme). Last season, he was outstanding and so far this season he's off to a good start. I would say he's been the best pick by Emery.
Long was outstanding his first two years, then the injuries hit and pretty much took him from a hall of fame projectory to now a decent guard. But a LT and a DB are more valuable commodities in the NFL than a guard even if he was a damn good one at one point.