We struggle with this as a family so much. I find myself referee and litigant in more device and console related arguments than I care to admit. It is maddening for me and Mr. T and it's no doubt detrimental for our kids.
I work with corporate customers to help them understand how to image, deploy and manage their devices and yet I struggle with setting and managing time limits and dealing with the pushback of multiple kids when trying to enforce reasonable balance. It's just plain hard. We have been plugging away, devising a plan that works for us. I've also been working on applying my technical knowledge to craft a homegrown solution for us which I will share when complete. Nothing wrong in fighting fire with fire.
One thing we have found vital is providing the equipment of fun. We received a most wonderful gift for Christmas of a field hockey (foosball) table. That table, with a nice fire roaring in the fireplace, some hot wassail in the decanter and fresh popcorn, are all a perfect recipe for an exciting, analog evening with the kids. Everyone loves to watch the heated games and partake in the smack talk. Mr. T has accused me of being a braggart but he's just jealous because I have yet to be beat!
Here's a great article about kids and setting limits on technology use.