Count me in. Thanks, Gandalf.nho.
I've never played any multiplayer one.
I like parties slightly better than single characters. But I like both. With parties, you seem like playing more roles, not just one. There'd be more character micromanagement, but I like managing things. Also, there'd be cooperation between party members which replaces the absence of other players in SP games. However you get roleplaying immersion with single characters. That depends whether the game has good story, details, or realistic enough.
Generally I prefer plenty of combat, as long as it's not too repetitive. Usually this is determined by combat mechanism, variety of enemies, style of how they fight you, variety of combat situations including locations. I very much like the possibility of unlimited enemies, means unlimited combat, means more XP, loot. But of course you can choose not to fight all the time, only when you want, at least after advancing well into the game. Take the Arena in Might & Magic for example.
Exploration is one of the most important aspect to me, because you're into someone's world after all. It has to be huge like real world. But this is only enjoyable if you can roam free in it. It's also great if you get a different randomized world every time you start a new game. It adds a lot of replayability. I like playing select few games with high replayability than playing a lot of games but you get always the same when you get back.
Crafting is always nice. It means more items possibly more nice artifacts in your game. You don't have to rely on loot or rare expensive artifact shops. It enrich the game a lot.
It's always nice to have some good minigame in-game. They're kind of distracting you from the world you're living momentarily. They'd be nice breaks in RPGs which tend to be long and exhausting. They also adds immersion too.
Just like open huge world, I love open ending for the sake of replayability and also that the decisions you make are determining how the story would develop. You'd be more considerate with your decisions and judgements. You'd face the consequences of your actions including your words. Just like in our real world. That would be a great immersion.
I also love it when you are not tied by time. You can end the game when you want to. I'm not so much like it if you have to finish the main quest, the main problem of the story ASAP.
Still not enough? :D
Just ask....