Lately I've been playing a lot of Perfect Dark (N64) which has quickly become one of my favourite games and had the chance for a quick go on Perfect Dark Zero while at a friend's house the other day. While I'm not sure I played enough to really know if it was that disappointing (only played two levels on co-op), it was - at least - a bit of a let down for a first go.
Anyway, I'm sure we've all played a decent first game and had a sequel disappoint us, so which ones stand out for you as being particularly disappointing?