The highest 3DMark Vantage scores are achieved by the Nvidia GeForce GTX 690: 46.538 points. The fastest single-GPU card is the AMD Radeon HD 7970 GHz Edition with 37.106 points.
You can see that performance has increased significantly over the past few years. In the same benchmark, an ATI Radeon HD 3870 scores 5.744 points and an Nvidia GeForce 8800 GTX 8.272 points. To put things in perspective, a GeForce GTX 690 is 161x faster than a GeForce 8400 GS.