Up Your Arsenal was easily my choice for best game up until A Crack In Time came out. I never played the online portion, but the story was fantastic and hilarious, there's a ton of worlds to explore, and the weapon upgrades felt great to pursue. My issues with most of the other games is they never hit the high bars set for content that these two had, and the story never seemed to hit the same highs either, either for UYA's humor or Crack's emotion.
Regardless, I think we can all agree that not getting another game for at least half a decade more really sucks.