I collected every book in Oblivion that I could find, brought it home, and stacked it onto the shelves. I didn't use any mod, so it took a lot and I mean A LOT of time. Of course, I read all the books. I collected different sets of weapons and displayed it around the house in sets. I explored every room of everything, I do it in every game, even the shitty ones.
In Assassin's Creed:Brotherhood I did all the missions with 100% sync and replayed some of them many times to get 100%. Also, I collected every feather, flag and treasure and have just a few more side missions to complete.
I didn't play more then 15 hours of ME, but I scanned every planet, read the info on all of them, and visited every one I could. Also, I read the whole codex.
In Dragon Age I explored every room, and took every bit of loot, so I had to go back and fort a lot of times. I read every bit of lore and any information that was in the game. I usually read everything, even in the MMOs.