Halo: CE had a fantastic single player.

Halo 3 has a fantastic Multiplayer.

Reach, well we'll have to see won't we lol.

If you didn't play them all and in the correct order an accurate opinion can not really be made.

I liked Halo 2 the best as I thought it had a great campaign and the online play was a vast improvement over Halo:Combat Evolved. Halo 3 has a horrible campaign with online maps that are more boring than 2's. Combat evolved is a fun rental!

none of the above, it's gna be the one coming out for the ps3!

Halo: Reach. No contest.

This. It has to be my favorite Halo by a long shot 

Reach is looking to be the best by far but for me the order is

Halo CE = Halo 3 / Halo Wars / Halo 2 / ODST

I like this MP but SP

Halo 1 > Halo 3 > Halo 2 > ODST.

I love them all so I hate having to find one better than the other.

Single Player: Who really cares?

Multi-player (the thing people actually care about): Halo 3

Halo: Reach is going to be amazing though.

works for me, i have more memories of 2, but three had some very nice addititons.

Halo 2 > Halo 3 > Halo CE > ODST.

I prefer MP to single play any day of the week so my list reflects that