I'll wade into this.
First, props for the reference to the McGill and Harvard games that was the origin of football as we know it today. I went to McGill, and know the tradition (but no, I never played football).
Second, the rules play an important part of the game. Like many have said, teams are built for a certain rule set. You might as well compare an NFL team to an Auzi Rules football game. Think Peyton Manning would have a chance in a game like that? No, he'd be knocked out in the first 5 minutes. Or think one of the big Auzi-rules players would have a chance blocking a DT in NFL-rules football? Not likely.
Third, Doug Flutie was one of the best QBs in the CFL, but only an OK QB in the NFL. Warren Moon was perhaps the best CFL QB, and was a solid NFL QB as well. Either of those guys would pick apart a college defense, but then again - those were the best. The current group of CFL QBs would probably be able to pick apart a college defense equally as well.
So, let's break it down by keeping things "Fair" - one game using CFL rules, one using NFL rules.
College players on a CFL field: I think the edge would go to the CFL team. Why? Better knowledge of the rules, how to use the larger field, and the strategies to win a 3-down game. They would also be more suited to the faster play (smaller OL & DL).
CFL Players on a College field: I also would give the edge to the CFLers on this. Many of them have "grown up" playing in the US College system (not the majority as there are "Canadian Content" rules for CFL teams). The keys to why the CFL teams would win: 1) Better coverage defense would make it harder for the College team to throw on them; (2) poorer college defense would allow the veteran CFL QBs to pick apart the defense over an entire game. I honestly think it would come down to those two areas - the CFL team would just out-defend the college teams.
Take that for what it's worth. I think experience would outweigh the pure physical tallent, for the same reason Doug Fluite "outplayed" Drew Breese early in his career with SD.