surely someone who sits in a room playing MMO`s all day is the archetypal loner??
for real immersion you need a single player campaign RPG with excellent story, controls and music. One that can be turned off and returned to when your fresh in the same position you were in when you left the game.
Some may argue there is a very strong social element to mmorpgs, especially where you are in a guild and doing all the mass raids etc etc. You can even talk to each other via team-speak/vent and so on. I knew people who would sit in the same room / house as each other and play, yet communicate through the game and headsets.
To get the most out of mmorpgs, you need to invest huge amounts of time into it. Not just tens of hours but hundreds or thousands. I knew plenty of people who played WoW and Eve etc, who had their total game time at well over 100 days (2400 hours). Once you have started a raid / world event or dungeon you are committed for the hours it takes. This takes, what could be considered the casual social element to the game, and turns it into a life sapping, antisocial monolith. This doesn’t necessarily make the player a loner but it does detach them from reality.
This is where Elder Scrolls is much better imo. It has a totally immersive gaming environment which you can pick up and put down at any point, saving where and when you like. The pause button is a great feature
Oblivion never really ran out of content either, say you put 100 hours in to complete it and do most of the side quests and missions. You can call it a day, go for 100% completion (if there is such a thing), increase the difficulty slider, re-start with a new character and so on. If you can do 3-4 runs through, then you could spend 300+ hours playing without getting bored. On very easy (slider to the left), you can run through oblivion in hours, set at medium (middle).
How much you get from RPGs depends on player motivation though and whether or not you are up for exploring and discovering the content. Some people are happy to run through the bare essentials and core missions in ~ 20-40 hours, complete the game and call it a day. This is still a good amount for a stand-alone, single player game these days. If you are only used to heavily scripted single player content you may not even look for more. People only seem to start looking for more content and missions if they like to get in to an rpg and not everyone is up for this or gets on with this type of playstyle.
Mmorpgs tend to lead you through more of the game content and quests, rather than relying on self-discovery and with something like WoW or LOTRO there are probably a good 7-10 days (240 hours) of linked and scripted content that you will be taken through without worrying about professions, reputations etc. Skyrim looks like a good few hundred hours of content.
With mmorpgs, life fits round the game, with rpgs the game fits round your life.