iPhone 5 16GB as a portable gaming device? I need help!

I seriously need help with replacing my DS, PSP and Nexus 4 with an iPhone 5 16gb mostly to use as a gaming device. I am now eligible to upgrade my phone and extend my contract and do not want to spend £150+ for a dedicated portable gaming device like the 3DS or PS Vita. Ive had them both for short periods and loved them but chose the Xbox 360 as a dedicated gaming device. The only reason I'd choose an iOS device over an Android device is for the gaming ecosystem ( I love the Nexus 4 and wonder whether the iPhone 5 can compete with it as a phone).

Are there really enough top tier games on the iPhone that can go head to head with a Zelda title, or Fifa on the PS Vita, or Metal Gear Solid Peace Walker on the PSP? Can the iPhone 5 work as a dedicated portable gaming device ready to be used for 1+ hour of gaming a day?

Can you please name the top 3 iOS games that you've put in 10+ hours in. And we're not talking about Angry Birds or Cut the Rope, we're talking RPGs, sports titles, action games, even a Mario competitor. I'd be mighty chuffed if i could get some help here :)