| How about Illuminatti?
Illuminati might fit your needs. Its not a wargame, but it does have competitive gameplay, as well as a pretty large amount of interaction. The core mechanic is simple, but there are enough modifier variables in the game to make things a bit more complicated.
The core concept is that each player controls an Illuminati group, and everyone is trying to control the world through a conspiracy network. Each group has a ranking for its Power and Resistance, an income, and possibly a number of alignments. Each Illuminati need to either control a set number of groups (dependent on the number of players in the game), or achieve a secondary goal unique to that Illuminati.
You gain groups by attacking to control them, which pits the attacking groups power rating against the defending groups Resistance (Power minus Resistance). Then the modifiers come into play. Alignments either create a bonus or a penalty. You can spend money to improve your roll.
The interactivity in the game comes from the other players at the table interfering in your attacks by spending money to worsen the attack roll. The game also allows for any form of in game deal that does not amount to outright throwing the game. This includes buying and selling groups and special cards. Or trading groups. Or paying someone off to attack a 3rd party. And no deal is binding unless it is immediate, allowing you to renege.
It is definitely more complicated than a typical Euro-Game.
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