I have a Colecovision but hardly play it. It does have some great titles though. But mine does have some sound issues so that may be a reason i don't play it much. I do think even it didn't have problems i'd be playing the Intellivision and 2600 instead.
Burgertime is great as long as you don't encounter the freeze glitch.
Turbo with the Steering wheel is awesome.
Centipede is unique looking, but i think it has a glitchy spider and not as fast the 2600 version.
Slither is a cool shooter like Centipede with the Roller Controller but you may want to mute the game, the sounds can get annoying after a while.
Squish em Sam is a underrated classic.
Cabbage Patch Kids is a simple fun game
Can't remember what Defender looked like but i thought it was a good port.
People brag about Mr. Do
Of course DK and DK jr are great. Some people say they were better on the 7800 though.
I want to get Frenzy, Pit Stop, Jumpan jr., Tutankham, Front Line, and a few others. Just need to to get the sound issue fixed. But i'm afraid it could cost more than just getting another system.
I'm not saying the Colecovision is a bad system, it's pretty good. But i do think it's overrated with all the hype it gets. Maybe one day i'll change my mind. Like i said there are some great games and some exclusives.
This has been the point of view of someone who grew up with an Intellivision.