Johnny Marr made The Smiths. Of course, Morrissey's words were always brilliant and funny and heartbreaking and literate and all of those things, but without Marr's music behind them, they would have been relegated to schoolboy poetry grade (see also: Morrissey's solo work). Marr somehow yinged Morrisey's yang.
On the subject of that other band; the Chili Peppers were (along with Nirvana) the first band that made me sit up and pay attention to pop or rock music. They'll always have that. And yes, they've released a lot of really awful music (see: some of their 80s output, the whole of One Hot Minute, the whole of Stadium Arcadium), there was something about their sound that grabbed me. I blew the dust off By the Way a few weeks ago and it really is a masterful pop album, so reminiscent of some lost great early 70s californian album. Even now, I'm still a sucker for Frusciante's signature guitar tone (that one that sounds like sun kissed palm trees in the Hollywood hills) and his harmonies on By the Way are superb. Going back some, Californication is a real hit-and-miss record, but has some inspired moments. Though I haven't listened to it in a couple of years, I maintain that BloodSugarSexMagik is brilliant. So yeah, Anthony Kiedis goofing around and getting a boner isn't too inspiring. But sometimes they overcame that enough to be quite awesome. Sometimes.
As for John's solo work, when I was 15 or 16, it was like having my very own Brian or Dennis Wilson. Super-obscure (despite being in what at the time were one of the biggest bands around) his (then) 3 solo records weren't really recognised by anyone, largely because 2 of them were out of print and supremely rare. Niandra and Smiles were attractive because they came from a place of darkness (even though like, every rockstar ever has done heroin, these somehow at the time seemed to rise above any kind of rock lore bullshit and appeared to glisten with artistic integrity and "authenticity"), were super lo-fi and mysterious, lending themselves to extreme scrutiny by a teenage fanboy. Of course, they had some real good songs on there too. So there it is.