Two and Half Men (Sheen era) is one of my favorite shows of all-time. I still watch reruns of those seasons. The Ashton era is garbage but this current season has been the best with him. Time for the show to go though. They should've made the show completely about Alan and not worried about bringing in a new co-star (The 'two and a half' could've been Alan, Jake and Berta

).
How I Met Your Mother is another GOAT. All that continuity and call-backs to previous characters & incidents

It's one of those shows that is really only funny if you've been with it from the beginning because you know the characters and events. You can't really pick it up at any other point and fully understand the show or get all the jokes. It did get weak for a few seasons though, I think part of that was they lost focus on Ted's story. The show is always better when it revolves around Ted, IMO. Barney is a great supporting character but he's had too much spotlight the last few seasons.
Big Bang Theory... I haven't watched any of the current season yet. IMO, Season 4 started the decline but the ratings keep getting better with each new season

. I didn't watch Seasons 5 or 6 all that closely but I plan on catching up with this season at some point.
Never got into Mike & Molly. 2 Broke Girls had some moments but not enough to keep me watching (didn't help that CBS.com wasn't posting full episodes online). I don't know of any other sitcoms they do.
HIMYM is ending this year. I would guess Two and Half Men is probably on the cutting block as well. I see the final two episodes of this season for 2.5 are "How to Get Rid of Alan Harper" and "Welcome Home, Jake". So maybe they are wrapping things up.
CBS was comedy powerhouse for a few years but they don't have anything to step up and replace those shows. They'll be in trouble next season.