Civ hot-seat co-op requires certain patience, especially during the end game, as one player has nothing to do while the other plays his turn, and a turn can take a while when you have lots of units to manage. That was the main reason we ended up buying another copy of the game, so each of us could play at the same time on our own laptop.

Civ IV allows the creation of teams, so you share everything with the other player. That offers a flexibility that I enjoy. For example, my wife always went for a cultural victory because she didn't enjoy wars, so when we played together I would focus on the military aspect and she would play as France or India and would build wonders for both of us.

The downside, in my opinion, is that Civ games tend to take forever, so that can be quite frustrating.

Btw, I am talking about Civ IV because I haven't played CiV in multiplayer.

It was already mentioned by someone else - but Magicka. Now that game is hilarious co-op. You should definitely get it anyways, it has been on steep sale more than a few times already - and i am guessing tomorrow might be the next...

Dungeon Defenders has that kind of local co-op referred to as hotseat/same screen/split screen

Thanks for the continued suggestions.

I guess I should clarify further what I meant by local co-op. I mean local simultaneous multiplayer - in other words, one PC, one screen, multiple players playing at the same time using multiple sets of controls. I don't mean LAN multiplayer. And I'm looking for a co-op game where the players work together to accomplish something.

Hotseat is another kind of local multiplayer. Hotseat is one PC, one screen, but each player takes their turn in the "hotseat" (single set of controls) while the other player waits. I might consider some hotseat games, but I think she'd get bored fast with those.

My recommendation would be Dungeon Defenders. Pretty sure it's still local co-op on Pc and is available as part of the Humble Bundle 7. :)
You should check out this website. They have a search function where you can specify what you are looking for. Hope it helps!

http://www.co-optimus.com/index.php