I went to Titan Fall after Halo (all of them) and was disappointed. Borderlands II and the pre-sequel were a cool substitute though.
Echo the thoughts of a previous poster that online can be tough. I prefer to play alongside mates against the computer. Running levels on Halo with someone who also knows the maps is laugh out loud fun.
The Spartan Ops (Halo) episodes that are available with an xBox gold account were great fun. I'm running them on legendary and getting killed a lot.
