The Yardbirds don't knock me out though. I love about 4 or 5 of their tunes and consider the rest filler to decent type tunes that I can tolerate. I bought 'Roger The Engineer' on peoples recommendations and it never hit me like it did some. I like it, but its nothing great.
The biggest problem of the Yardbirds is that they never developed as good songwriters. During their first years (1964-65), they recorded songs by other artists or written by outside songwriters like Graham Gouldman, with few exceptions like "Still I'm Sad". The material was not great but good enough, and the amazing instrumental talent of the band plus their experimental vocation converted them into one of the most influential bands of the mid-60's. Their biggest hits ("For Your Love"; "Heart Full Of Soul"; "Shapes Of Things") stand as truly high points of the decade.
After that time of glory, they started to write their own material from their first proper album, Roger The Engineer
(1966). That album is acknowledged as one of the first strong steps of psychedelia, but the songwriting was very weak and the great performances couldn't save it, in my opinion. A similar problem occurred in their next and last album, Little Games
I love the Yardbirds and still consider them an essential band of the 60's. But I think that a compilation focussed on their mid-60's work is enough to taste their magic.