These three have global infrastructures and I think all three have their own direct connectivity to Eurex so all three of CQG, TT and Rithmic at least should be good choices. Most of them have connectivity architecture details on their web sites that you could look at. I am sure you could have a whole thread on which is best for Eurex (or any other particular exchange).
Do you think that TT has more instruments than Rithmic? I guess that some of the foreign ones may be academic because most U.S. users would not be allowed to trade many of them anyway under S.E.C and CFTC restrictions....