I always love these topics since I'm 50 -- there's inevitably music from younger folks I will find mentioned that I've not heard, will listen to, and then really like. Maybe you'll find some here, though some of this is pretty mainstream.
I went through my several hundred albums list and came up with this -- these are albums where I think the band's best (or, in some cases, only good) album is their debut:
Sex Pistols -- Never Mind the Bollocks
Gang of Four -- Entertainment! (still pretty much my favorite record of all time)
Wire -- Pink Flag
The Ramones
Liz Phair -- Exile in Guyville
The Screaming Blue Messiahs -- Gun Shy
Sugar -- Copper Blue
The Stone Roses
Archers of Loaf -- Icky Mettle (most underrated band of the 90s IMO)
The Tubes
The Strokes -- Is This It
Weezer (the blue one)
Honorable Mention
The Dead Kennedys -- Fresh Fruit for Rotting Vegetables
Van Halen (tough one -- I might be the only person in the world who might like Van Halen II better)
These are other debuts I think are pretty good but these bands have better albums that came later IMO:
The Clash
Steely Dan -- Can't Buy a Thrill
REM -- Murmur (although the EP Chronic Town was technically before it and I like that even better)
The Psychedelic Furs
The Police -- Outlandos D'Amour
Foo Fighters