Final Level: Orphan's Cradle
Why It Sucked: What a mess. FF XIII was such a slog that we didn't give one hoot about the ending by the time we finally got there. Fang and Vanille's self-sacrifice felt meaningless, and never before has an FF game been so blatantly set up for a sequel.
How We Would End It: We don't really feel the need to come up with this part, since Square Enix already did. They named it Final Fantasy XIII-2, and it's got some pretty convenient time travel loopholes.