Something Bad About The Halo 2 Ending

ICESPIDE says:

just finished halo 2 and for what? the worst ending in the history of video games. what a huge tease. really pisses me off. of course i didn't throw it away, it still kicks ass on XBox live. I hate it when developers end games horribly just to garauntee a halo 3. ugh

I have no idea, but considering the big plot holes in the first one I can only imagine it to be a very bad thing i.e unresolved assault on Earth.