Acts whose debut album is an afterthought in their overall discography

o it's already been broughten

Lauper was the lead singer of Blue Angel, so would be a different category as noted above, re Debbie Harry in pre-Blondie band The Wind In The Willows (also as noted, the album by Blue Angel is good, with Lauper's 50s-80s belting in a no-frills club rock setting).
Haven't heard Alice Cooper's xpost Pretties For You, but used to play Easy Action and thought it was pretty okay: a bit demo-y, but Vince's vocals really go for the gusto, as they used to say in that beer commercial he probably relished.

Did anybody mention these cobbled-together collections that can come out soon after the first proper albums hit it big, like Hendrix on sessions of Curtis Knight, Little Richard, the Isley Brothers (got some of the first two, would love to get the remixed tracks, with guitar highlighted, that the isleys bought out on their label: really good reviews, OOP forever, prob 100s of dollars on eBay)

since somebody mentioned it...

http://www.willardswormholes.com/wp-content/uploads/2010/11/cover1-293x300.jpg

Inquire within:
http://www.willardswormholes.com/archives/468

does the Jefferson Airplane debut count?

no, but the first Jefferson Starship album (Blows Against the Empire) almost does....

Jefferson Airplane Takes Off is a solid debut, and neither fans nor the band distanced themselves from it. I think of it like the first Fairport Convention album (which sounds surprisingly similar, and is also very good); each was made with a fine female vocalist who left after the first album and are unfairly maligned because they're not Grace Slick/Sandy Denny, and weren't as popular or quite as good as what followed.

Gerry Rafferty's Can I Get My Money Back? (1971) is a weird one. Tucked in between the three Humblebums albums that proceded it and the three Stealers Wheel albums that followed, it was ignored upon its release and still (undeservedly) gets little attention now. It would be another seven years before City to City, which topped the charts in the US and many probably think is his solo debut.

John Cale's Vintage Violence fits doesn't it?
Think it's his first, stylistically different etc. VU were still obscure when he left.
Not sure what's on it though, so he may have reworked songs live.

First Little Big Town album (Monument 2002) also fits.

Did Dead Can Dance get a mention already?

First two Sparks albums? No hits on either of them, recorded with a different band to the "classic" era, and I guess most people assume their recording career started with "Kimono My House".

What about Mark Everett's pre-Eels solo records? I guess "Bad Dude In Love" probably doesn't count as it was self-released and obscure to the point of being an urban legend, but "A Man Called E" and "Broken Toy Shop" must do.

Yeah did think of those, they're a more pop version of himself..

Suave House released an album Rick Ross recorded back in 2002-04 ("Rise to Power") after he dropped Port of Miami.

"Genesis - From Genesis to Revelation"

def