There is a brewpub next to Six Flags called Humperdink's that has a shuttle service. For $15 a person, you can park at Humperdink's, ride the shuttle to the stadium, watch the game, and then ride the shuttle back to Humperdink's. So, if you don't have a large group, this could be a good option for you.
My son and I used this service last year for the Thanksgiving game (Chargers vs. Cowboys). We paid $30 bucks and only had to walk three blocks or so to meet up with the shuttle. Much better that paying $100 for parking. In fact, we live in Arlington and it was still worth it to pay the $30 to use the shuttle service instead of trying to have my wife negotiate the horrendous traffic to drop us off and still have to walk about 1 1/2 to 2 miles to get to the stadium entrance.
Here's the link for more info:
Humperdink's Shuttle Service