One aspect that I love about RPGs is the ability to have followers tag alongside with the player. Not only do they provide assistance in combat, but they also carry their own backgrounds and stories that players can learn through dialogue and quests. I loved learning of Craig Boone's story in New Vegas and discovering why he is so distant and bitter through questlines and interactions with other characters. I also loved Cass' crude humor and her frequent comments about the locations that she and the main protagonist visits. I find that details such as this make RPGs feel alive.
This is where I find that Skyrim terribly dropped the ball. The followers were some of the blandest characters I have ever encountered in any video game. Not only were they devoid of any personality, but most of them had no substantiall story or background worth remembering. Maybe the sheer number of followers in the game is what caused the lack of substance in the characters. It's as if Bethesda went for more of a quantity over quality approach for them.
I will admit that I feel Serana's introduction was a big improvement. She had a friendly personality, a detailed background, a compelling story, and a questline made just for her. The thing I liked the most is how Serana interacted with the environment. She would complain about the weather and wear her hood during day hours, she would make unique comments about the cities she visits, and at she would interact with workbenches, labs and dinner tables. She actually felt like a living being instead of some synthetic pack mule like the other followers.
I hope Fallout 4 has companions similar to the ones in New Vegas and Serana in Skyrim. They should have vibrant personalities, interesting stories, dedicated questlines, unique dialogue, and advanced behaviors that makes them seem alive. They shoud be more than just pack mules that lug around your equipment. A game can have all sorts of fancy features and graphics, but that does not do much if the actual world itself lacks any form of flavor.