The risk you run with any NOFX album is that it's almost guaranteed to be 50% garbage, but I have fond memories of Punk in Drublic (disclaimer: I haven't listened to it in over 1/2 a decade, at least). I know you already listened to at least a few song off So Long...
Other bands, you've got the well known guys like Anti-Flag (they've always been catchy as fuck, but American Fall has some next-level ear worms), Bad Religion (Generator through Stranger Than Fiction are probably their strongest albums), Pennywise I know you've listened to, Strung Out has some good stuff (An American Paradox was a favourite of younger Geoff, and revisiting it now, it's still a fun album).
Good Riddance leans a little more towards the hardcore end, but they're still one of my favourite bands. I'd recommend checking out "A Comprehensive Guide to Modern Rebellion" and "Ballads from the Revolution"
The Lawrence Arms (and associated acts Slapstick!, The Falcon [1/2 Lawrence Arms, 1/2 Alkaline Trio members], and Sundowner) are pret