The Most Universally Respected Bands (among metalheads)

in addition to the bands already mentioned

Enslaved (most people respect them, even if they are not that much of a fan)
In The Woods... (almost all people who know this band admire them)
Blind Guardian (never seen anyone really bashing them)
 
Blind Guardian (never seen anyone really bashing them)

You'll find plenty of haters if you ask about them, myself included.

Other two are fairly sound suggestions though.

A fair bit of trad. doom seems to get all-round respect. I don't think I've seen a bad word against Saint Vitus, Pagan Altar or, to a slightly lesser extent, Candlemass
 
Most universally respected, I'd go with Maiden.

Agree with the majority here, but Ill throw out

Isis? Anyone who's heard them in my experience has nothing but good to say.

Iced Earth?
 
Most metalheads like Megadeth.
Seems like the universal vote. Also I've never heard anyone mention they hate Hypocrisy either. Peter Tagtgren is not only respected for his music but his superb production skills.