(sorry that this is obscenely long, I might have a problem)
1: There's something for everyone!
Do you like edgy emo music? Listen to Pinkerton! Do you like formidable pop-rock? Listen to Blue Album or White Album! Do you like hard rock or something metal-adjacent? Maladroit may or may not satisfy you! Do you like orchestral music? OK Human is an honest-to-God masterpiece! Do you like stupid weird bullshit? Listen to Red Album or Hurley! Do you like just completely straightforward pop songs? Listen to Pacific Daydream or Van Weezer! I could go on and on and get even more specific, but I'll spare you at least that much.2: They're insanely well-documented!
Do you like absorbing every little facet of information about a band? You can find hyper-specific information on absolutely every era of this band!! Weezerpedia, an entire wiki just for Weezer (and a few adjacent bands), has 7500 in-depth articles about every song, every tour, every member, every demo... did I mention demos? Rivers Cuomo, the frontman and main songwriter, has made over ten thousand demos from as far back as 1988 available to buy on his website (or I could send you the Dropbox links because who cares lol). Almost every song the man has ever written is publicly available to listen to, and a huge chunk of the songs that never made it on an album are outstanding in their own right!!3: They're actually on an upswing!
Weezer has been much-maligned over the years for being past their prime, or peaking with their first two albums and only making crap ever since. This is simply not true. I must admit, first, that they did kinda fucking suck in the mid-late 2000s and late 2010s. (They did have a few hidden gems in this era, but that's besides the point right now.) Right now, I would honestly say Weezer is the best they've been since the 90s. Their live shows have some actual energy and variety pumped into them after a decade of limp greatest-hits sets, their new songs are reaching heights we thought they never would again (my personal favorite Weezer album, White, is only 9 years old), all those demos I mentioned earlier were released fairly recently, and Rivers Cuomo has a public Discord server, for God's sake!tl;dr: start with the first two albums and then skip around depending on your preference, at least give em a chance