Well, if you are a fan, you pretty much know the deal.
H is "perfect" and super-clean.
Also an excellent writter of body and leads.
Davey is as Caveman stated, "creamy".
He is so unique and gifted, how could you top him?
Dennis is awesome. The first album is permanent proof of his blissful abilities.
Bruce? Please. One crown is enough for any man!
Jannic (Janick) Gers is also like K Shirley put it, "Dangerous" playing stuff "outside the box".
His writting is crucial to the band, his contributions are very highly, highly valuable!
His playing live is a bit sloppy, hard for us early 80's fans to accept having been brought up with the guitar team from heaven!
However, his energy and stage pressence is unbeatable.
Altho it bothers me about stuff like 'Lord Of The Flies' timing issues (is that a Jannic thing? -I can't imagine Davey or H doing that?), Jan is, I'd say, extremely valueable to the whole Maiden package!
So, they are all great!