Josh always explains his Manowar stance pretty well, so I'll steal it.
The problem with Manowar is that they have great potential to make incredible music. They've written and recorded some great songs and they're all very good musicians. Unfortunately, "things happen" and their last albums have sounded god awful. You can still hear the potential so I don't know if it's Joey's ego getting in the way or what, but you're right, they are a great band and capable of doing great things.
...and then you get those last few albums, and it's all very confusing.
The difference between them and Edguy is that at least Edguy is in on the joke. Manowar currently makes hilariously terrible music and thinks it's the best thing ever.