Arkham is the great blob king of shitty boss fights. Gigapede is also terrible. What of it? It's two out of 16 total fights. Anyway, if you're trying to argue DMC3 has worse bosses than DMC4, 4 still has plenty of shit boss fights. The danger room, Sanctus, and the fucking Savior are almost as bad as Arkham.
Yeah, it's a lot more than two. The only DMC3 bosses who let you go nuts are Agni and Rudra, Cerberus, and maybe Beowulf. The rest all have stupid conditions you need to fulfill to do damage to them or just repeat patterns over and over again. Nevan is repetitive, Doppleganger is really boring, Geryon just runs in a circle, Leviathan Heart doesn't even attack other than shooting lasers, Lady just runs away and has you fighting the camera and the room layout as much as you fight her. Weaknesses make no sense (why are 4 or so bosses weak to Cerberus, anyway?), and often the most-effective strategy is just to jump-cancel Aerial Cross as fast as you can. They're not broken or really "bad"," but pretty boring, especially compared to the standard combat.
I would rather fight Berial than any of the DMC3 bosses. DMC4 has less bosses, most of whom (Credo, Berial, ice frogs, Echidna, Dante) are all pretty interesting and varied. Sanctus is stupid and the Savior is awful, but it's more of a terrible level based around the Savior than an actual boss fight.