How I Met Your Mother fails to engage me every single time I tried to get into it. So I guess it does suck. Although I have never endured a full episode.
The Big Bang Theory isn't that bad, the idea of nerd being mainstream was finally fully exploited in that show. It was refreshing for once seeing more introverted-ish people in TV instead of people who always party, that's my opinion at least
Do Disney shows count as Sitcoms? If so everything recent but Good Luck Charlie is crap there.
From the ones I watch/watched, I would say How I Met Your Mother. First 5 seasons were good, then it went downhill and people who came up with the series finale need to be punched in the face.
