Honestly, if you simply look at the statistical compilations, Ben is easily among the top 5 QBs right now. We're talking TDs, completion percentage, YPP, QB rating. All of it. And that's just his contemporaries. Statistically Ben is actually in some categories among the best ever to play the game. He's not the top QB across all categories by any stretch of the imagination, but he's ridiculous in YPC (Catch). Ben throws the long ball with more regularity and completes it better than ANY of his contemporaries.
Brady may be "accurate on the deep ball, but he throws deep MUCH less regularly than Ben. (And by "deep" I mean 15 to 20 yard passes). Brady's completion % is better, but he throws (literally) 3 and 4 yard passes a large chunk of the time. Ben more often throws 10 to 25 yard passes. And completes them nearly as often as Brady's long handoffs. There simply is no comparison.
And if you were to factor in intangibles on top of the standard statistical factors. You'd have things like John Elway's "helicoptor for first down" which helped will his team to a Superbowl victory. No QB in the modern era has shown the Tarkenton-like ability to avoid pressure in the pocket along with the sheer toughness of Steve McNair to take a hit and shrug it off while extending a play for a huge gain downfield. Admittedly this is actually both a strength and hindrance to Ben's game, but it forces teams to play him differently because the defense has to both collapse the pocket AND contain the scramble AND maintain coverage on receivers downfield. There's nobody like that in the entire modern history of the game. And you'd probably have to look pretty far back to find a reasonable comparison in the golden age who had the accuracy and the vision that Roethlisberger has developed as he's matured.
No. He's definitely among the best in the league and one can easily argue he's among the best who's ever played.