I found this recipe on Cooks.com and have not tried another marinade since (its called "Grilled Steak Marinade" if you want to check it out there). I have made this for my wife and I and large groups alike; everybody has LOVED it and asked me for the recipe. I am begging you to try this, you won't regret it.
I got this recipe from my mother- its easy, delicious, and makes great leftovers. We make a batch and then scoop 1 cup portions into tupperware to take to work all week.
Its a guaranteed pleaser for even the pickiest eater. Kids love it too. Enjoy!