For weekend games, there's no argument....there should be trains for every game on every route. (Heaven forbid that we just run them year round, and people find them useful for all the other things that go on downtown in the afternoons!).
Night games are a little different, in that until you have 2-way capability it will be glaringly obvious that there is no inbound service. Lots of people drive to Lakeshore GO stations for this reason....happily, the parking lots are clearing out late in the day so they park for the game and drive home from there.
I bet you could fill an outbound post-game train on each line even so....people will still trickle downtown during late afternoon on bus, etc.
- Paul
PS - the biggest value of the added Lakeshore trains is the ability to move the "next train" into the depot right after the last one leaves. There's half a hope of the platform still being mostly empty, hence the move is much safer. If you wait for the next regular train to arrive a half hour later, the platform is packed.