I do think Portal 2 was a bit overrated. I'd have put Borderlands 2 (or just the Borderlands series as the Pre-Sequel and some of the expansions were also good) at the top. As far as Diablo III goes, I got way more out of Path of Exile for less money. Diablo III is a lot simpler so it's good if you are playing it with younger family members. PoE is more like Diablo II modernized with a seriously advanced skill tree. I am not sure how Don't Starve Together got on there. There are some good titles in that list though. I was a bit surprised at the lack of procedurally generated voxel games, but then again it wasn't meant to be an exhaustive list or anything.
StarCraft 2 has been one of my favorites lately. It's the only RTS game that I know of that has specific co-op missions and commanders. Reminds me of Red Alert 3 and it's co-op only campaign which was super fun, but is difficult to get working now that you have to use 3rd party support to replace gamespy.
Must have been a rule on the age of games checked, because there's no sign of SWAT 3 or 4 on the list. That was true co-op play, & even in the "deathmatch" style games a team was rewarded more for arresting an opponent vs. just killing them (1 point per kill vs. 5 points per arrest). Not to mention the very different "VIP Escort" mission, where the Tangos couldn't kill the VIP before a) arresting him & b) the 2-minute timer reached zero; killing him before that point lost them the match.