I'm not a fan of racing sims, but GT5 had a nice charm about it. The music, the menus, the graphics, it was definitely a good few months playing that game with my friends.
...But, it felt incomplete, it felt like 1 years work, but it wasn't, it was 6 years work. GT5 was a disappointment on so many levels. When I get round to trying Forza 3 or Forza 4, I honestly think I'm going to prefer it.