I like open world games, but the focus has to be more than just space available. Back in Ultima 8 (and even Ultima 9) you got the ability to climb stuff which, while limited, was something that wasn't big in RPGs before or since. Take Morrowind, Oblivion, or Fallout. You never actually get out your hands and climb, you just jump up against something - you don't even dive. It's frustrating because, like in silly old 2D RPGs, you end up getting held up by some debris about waist high. Plus, it takes strategy out of the terrain. For instance, being an archer or sniper would mean a lot more if you could put yourself in a relatively inaccessable location to ambush a target. Really, I'd like to see an open world RPG incorporate some of the movement and climbing aspects of Assassin's Creed into its framework. That'd be fantastic.
Also, we need some more interaction in these environments. I hate coming across useless or static junk. I'd love to be able to use spells or powers to do different things. Using physics to damage people would be great. For instance, if I set a mine and covered it with debris, you'd think that debris could cause some damage. Or maybe I use a levitate spell to suspend a barrel of flammable oil over a fire until some enemies show up, when I drop the barrel so that it shatters and scatters burning oil all over. Maybe I can even set a forest on fire like that. Just let me do unique stuff, so that there's more to the environment than just static objects or useless rubbish.
Finally, give me back the damn party. In Ultima VII and Baldur's Gate you had a party of characters that kept you company in the otherwise lonely game world. This serves two purposes, really. One, you get to choose some companions to come along. I like when they can be either in-game NPCs or user created, just because it's a nice option to have both. Still, the number of people has to be three or more, and it has to be from a pretty good selection. I hate my companion choices in Fallout 3, for instance, and I'd much rather have the Baldur's Gate variety. The other good thing about parties is that you can not use them. Baldur's Gate II, for instance, is a lot of fun to try and play as a solo wizard... because it's not easy to take down a dragon or lich by yourself. It adds a cool challenge when you're doing things solo that were meant for a party - just make sure I get more experience (or whatever equivalent) for doing it this way so I feel rewarded. An important side-note here is that scaling the level of the loot or encounter to the player is lame. I should get to choose how easy or hard I make the game. If I want to raid the hardest areas in the game right away, let me do it and get a good reward. It's great to challenge myself this way.
