I'd probably put Melrose Place here. Horrible show, but I was so addicted to how trashy it was for a long while.
Really hard to put anything else on a "can't believe I liked it" list because the stuff I watched when I was young is stuff I don't look to catch back up with (like, I'm sure I'd think the Cosby Show was pure sugary crap now with really disturbing undertones due to what Bill wound up being, but when I was a little kid, it was THE SHOW). And with other shows, it seems like if it doesn't click or it stops clicking, I stop watching. Maybe a couple of those pseudo-reality shows I've watched from time to time with friends while drinking, like Wicked Tuna and whatnot. Dumb as fuck, but under the right conditions with friends and intoxicants, they can make an evening go by quickly.