Very few. When I've played games like poker and Monopoly I've seen new players struggle with the (relatively simple) rules so I was comparing this game to those.
Monopoly is rather complex for the relatively small dose of fun it provides. Poker is quite simple in its base form, so I'm not sure what to tell you there.
Codenames is quite good and is available from Target.
Love Letter is a modern classic of tight, simple design.
These are two examples of what I would consider gateway games for people who have only ever heard of Monopoly or Trivial Pursuit.