Ultima 7 was awesome.
But I feel open-world RPGs are starting to become an oxymoron because it is a sign of the times. I find myself enjoying more "close-world" RPGs like Mass Effect 2. Themeparks are starting to become more enjoyable for me.
I just finished LA Noire, but I am more interested in the story than exploring the whole of LA. There's just no reason to explore. Nothing happens outside the street crimes and main story.
Or maybe it's because open-world RPGs are not done right. I remember it was interesting to explore Ultima 7 because I'd never know what I would find in caves. I may find more magic armor, magic weapons (such as the fire sword that also acted like a torch), treasure in the form of gold bars, jewelry, dragons that drop jewels, interesting creatures like that Unicorn that is a virgin-detector lol, the Cyclops that could talk and ask the Avatar why his people were always the target of genocide, the crazed sultan suffering from delusions that had the powerful stone harpy guarding his treasure, etc.
In Skyrim there is no such incentive to explore.
Huh, odd. It took me forever to get around to doing actual quests with my first Skyrim character, because I constantly got distracted by exploring. And I found plenty of interesting & useful stuff in caves. Plenty of stuff that wasn't new or interesting, too, but that's normal for RPGs with lots of loot. (Even roguelikes like Diablo, that can churn out millions of different Prefix Swords of Suffix, the vast majority of stuff you find is junk that won't be useful to you.)
Yeah, there aren't many "scripted" things, like wacky NPC encounters, but there's certainly plenty of reason to explore.

(And yeah - I played Ultima 1 throught.... 6? 7? back when they first came out. Until the series stopped publishing for the Apple 2. Good games.)