Better in what way? Not a phone on the market has a screen to match the OLED on the vita or the graphics it can produce. I have yet to find a game on a mobile device that plays as well as something on my 3DS or Vita.
There are 5" phones with 1280x720 and 1920x1080 now. Graphics wise the upcoming tegra 4 and powervr 6 series will destroy this gpu. The only advantage of this over phones is that the screen is OLED and there are physical controls.