I remember reading a review of a game last year where the guy's girlfriend was playing it, without any of the preconceptions that us gamers grow up with. She kept asking questions like "But why can't I do this?" "How did you know I'd be able to interact with that?". As gamers, we've learned over time subtle things like "objects looking slightly different usually mean you can interact with them". Weird West is one of the first games that I feel really starts to break out of that; if you think "I wonder if I can..." the answer is probably "yes". Aside from the very detailed simulation of the Weird West, there's also bounties, combat, stealth, looting, quests and a really excellent story.
It's one of those games that even at the end, I was still thoroughly enjoying the ending, rather than wanting it to be over. The last 5 minutes of the game are meaningful, explain the story, and give you interesting choices.