He has a point about the villains, though. Liquid Ocelot has several stellar moments, the kind that you would expect from a really good villain typical from a mindless action movie. But when it comes to his actual character, he's nowhere near MGS2's Solidus or The Boss in MGS3. Crap, he isn't even near his MGS1 counterpart. He lacks any kind of character development, and his true motives (I mean Liquid's, not Ocelot's, which differ from each other) are hardly touched upon.
And don't get me started on Vamp. I always thought that Vamp in MGS4 would be some kind of wildcard; a villain that is on his own, trying to screw up both you and Liquid now that he has nothing to lose (since he lost all his loved ones in MGS2 and, well, can't die himself). But Kojima actually made him into a generic henchman with no motives whatsoever, following blindly the orders from the same guy who fucking shot Fortune in MGS2 (I know, technically it was Ocelot who shot her, not Liquid, but it's still stupid).