I should first say that going to a chain restaurant is a hassle/chore for me, and not something I'd CHOOSE to do, especially not on a special occasion.
That said, I've found things that are tolerable to eat at Olive Garden, Macaroni Grill, Red Lobster (the butter isn't real, but they usually don't overcook their veggies which is nice), and Chili's/Applebee's/Ruby Tuesday's (I consider them the same restaurant; I'll eat steak, a burger without a bun, or a salad after a little customization, and at least one of them has ribs with a dry rub that I actually like). I pretty much just order a dish where the meat sounds like something I'm willing to eat, and ask for vegetables instead of whatever else it's supposed to come with.
If it were a really special occasion I'd let myself "cheat" for the one meal. I'd probably pick sushi, thai, or a nice upscale Italian place (where I'd be able to stay primal if I really wanted but would probably eat a few bites of pasta). And I'd get dessert. But that's me. =]