[quote name='hosslogan']So, should I go with used or previously viewed? I really like my games to be complete, if at all possible.[/QUOTE]
No guarantee either way. Personally I go with used on the basis that rented games have passed through more hands and should generally be more messed up (but I really don't know if this is true). However, I don't think you should really worry either. I've bought a ton of games from goHastings (over 30), and I believe they've all come in complete, though a couple came in rental or damaged cases. Additionally, the actual games themselves have all been in pretty good shape, sometimes perfect.
This applies mainly to current gen systems though. Probably a much greater risk of obtaining incomplete games for older generation games.