When people argue that "app" games are as good as PlayStation or DS portable games, they'll usually whip out a racing game, and with good reason: iOS and Android's racing games are actually some of their best games, period.
GOLD MEDAL: Real Racing
The best all-rounder in the App Store today, with great graphics, good car and track choice, multiplayer support and respectable realism combined with arcade-feeling, usable controls. This is a fairly straightforward racing sim, but one that never veers too far into car nerdery or dumbed-down, racing-one-rails action. My only complaint is that it isn't universal, so iPad owners will need to buy a separate "HD" app. $6, iPhone.
SILVER MEDAL: Crash Bandicoot Nitro Kart 2
Let's be honest about this whole "racing game" thing: It's got a somewhat limited appeal, especially when you start looking at hard racing sims. But everyone - EVERYONE - loves Kart games, and Crash Bandicoot 2 is the best on the platform. If you've ever enjoyed Mario Kart, you'll probably like this. (Though that's sort of like saying, "If you're a human being...") $4 (discounted to $2.49 for a limited time), iPhone.
BRONZE MEDAL: Rally Master Pro 3D
A game for people who like their racers slippery. Despite handling a good deal of the control scheme automatically, this is actually a fairly authentic rallying game in that the focus is almost entirely on nailing difficult turns. $6, iPhone.
Others • LilRacerz Pro: Don't be fooled by the cartoonish graphics, this free top-down racer is a deadly serious timesuck. • Parcel Panic: The iPhone's only true spiritual successor to Crazy Taxi. • Drift Mania: They made a movie about this! The game is better than that, at least. • Asphalt 5: A pretty - and pretty bland - racer from the ever-reliable game mill Gameloft. • Need for Speed: Shift: I'm a fan of the NFS franchise from way back, but something about this game's mechanics don't feel quite right to me. Also, it's 'spensive! • Reckless Racing: I have a feeling this top-down 3D racer would have taken the top spot, if it were out. It's not, at least for a few days.
GOLD MEDAL: Asphalt 5
As far as Android racing games go, Asphalt 5 is the pace setter. The 3D graphics are stellar, the controls are just right and the gameplay is action packed (sound is a wee bit annoying, though). Asphalt 5 is geared more towards the arcade racer (think Ridge Racer) than simulation racing but you still get three very accurate control options: accelerometer, wheel or tapping the screen. The game can only run on higher end Android phones (think Nexus One and above), so you might have to think twice about the purchase but if you do have a good Android phone, the replay value of Asphalt 5 is amazing: there's a career mode to collect money and trophies, various challenges and in-games, and each car (and there are over 30) can be customised with engine upgrades, paint jobs and decals (feels good to pimp yo ride). ~$5.06, Android.
SILVER MEDAL: Need For Speed: Shift
Honestly, Need for Speed: Shift is a gold-medal driving game. Its detail in its graphics and buttery smooth gameplay is arguably better than Asphalt 5. However, NFS:Shift isn't readily available for all Android phones in the Android Market (it only comes pre-installed on certain phones) which is terribly unfortunate for racing fans. ~$10, Android.
BRONZE MEDAL: Raging Thunder 2
The 3D graphics aren't as good as Asphalt 5 and gameplay can lag a bit but it does offer online multiplayer mode and a fast-paced, arcade style gameplay that's either fun as hell or a little bit tacky, depending on how you see things. ~$5.06, Android.
Others • Speed Forge 3D: A 3D jet-racing game that's limited because it only has three vehicles and six tracks. ~$2.82. • Xrace Beta: Simple and free racing game but has unimpressive graphics and only works on Android phones with a keyboard. Free. • Light Racer 3D: A Tron-styled, motorcycle racing game that can be played multiplayer over Wi-Fi. Free or ~$2.52. • Craigs Race: Basic 2D racing game that's fun the first time, but then gets less and less enjoyable the more you play it. Free. • Pocket Racing: Topdown 2D racing game that's surprisingly impressive (to a point). Comes with five cars and eight tracks. ~$1.59.