YMMV on that one.
Personally, I felt that KotOR 2's story was rather a mess due to time constraints and overreliance on a single NPC, NWN 2 's story had lots of boring filler content and was overly reliant on a ridiculous NPC who might as well have been named "Plot Device", and Alpha Protocol's story was horribly clichéd (though I liked the game overall as well).
Dungeon Siege 3 is primarily a hack & slash though, so I doubt it'll have that great of a story; it's just not the point of that kind of game.
New Vegas was great, story and all, though. It helps that the story was largely recycled from Van Buren, when they apparently had better writers than they do now.
Having said that I would like someone using the Planescape setting again, but I doubt it'll happen, and even if it did I'm not sure even Obsidian could do it justice as they are now. Remember that they'd have to use D&D 4th ed. rules, too.
You must consider that Avalone not always is writer for their stuff.
He wrote Planescape, he did new reno and vault city dialog and stories in F2, He did most of dialogs and story in New Vegas. led the design of the cancelled Fallout title Van Buren. And he is creative director and main man behind Dead money DLC for New vegas.
He has great talent fr his work.
But he isn't always involved in stories or dialogs. Sometimes only one of them.
Planescape is 1st place in storytelling and narrative of all games. Till this day i can't comprehend how some man can create that awasome story.
Great stories rarely consist of big WTF moments (in a good way) and they hount you for few days after finishing game. Like The boss story in MGS3.
Planescape is one big WTF moment one after another and ravel, immortality, valor, dakon story etc . ending, crypt of immortal, Nordom ignus story, changing your body, tatoo meanings, whole world of planescape torment at the begging felt like you found a diamond in big pile of shit that was gaming back then and even more today. The more hours are passing the more you are amazed. And in end game moments story is WTF WTF WTF WTF WTF to the end. -
Sad part is probably we will never see again game that is this good in story department.