After thinking about my recommendation for Through the Ages, it occurs to me that you and your wife might be well served by a wide variety of eurogames. Many euros have very low player interaction, and while not exactly cooperative, they certainly avoid the "beat up the other guy" problem. In fact, many of the best-regarded euros have been accused of being "multiplayer solitaire", an accusation which might turn out to be a ringing endorsement in this case.
The interaction between players in many games comes down to denial-of-choice or denial-of-resources. For example, in Puerto Rico, if you choose the Craftsman role all players will produce goods, but you'll get an extra for choosing the role. And in Agricola, if you go fishing no other player can get food from fishing that turn. In both cases, you've denied the other player the opportunity of making that choice.
Those are three of the best games in the world (don't just take my word for it, ask BGG), and big favorites at my family's table, which often includes just my wife and me. I answered originally with some strictly cooperative games, but thought you might enjoy the low player interactivity of these exemplary eurogames, too.