It's hard not to compare games, but with games like Forza Motorsport 4 and Gran Turismo 5, it's nearly impossible to avoid. So here it is, put simply: Forza 4 is both a strong competitor for GT5 - and the total antithesis of it - in all the right ways.
From the moment Forza 4 boots up for the first time, the design philosophy is clear: Let players play how they want and never get in the way. After an exciting Ferrari race in the Alps, Forza dumps you into the menu and the world is yours from there.
Head for career mode, check out the free play, or jump right into the online modes. Once you're in, you can select your difficulty - just like in Forza 3 - down to the minutest of details. Braking lines, traction control, steering and more let you decide whether you want to just steer the thing or whether you want total control of your vehicle at a close-to-simulation level. Unlike past Forza titles (not to mention Gran Turismo), Forza 4 doesn't seem to care much what car you want to drive, aside from forcing you to raise the class up with the difficulty. As long as you keep upgrading your vehicle, you could drive the same car from the first race through the next couple levels.

My first thought was that this was almost a negative in a way - I'm not being challenged to try new cars the same way Gran Turismo tends to do or even the way Forza 3 did to a lesser degree. Then I remembered: I quit Gran Turismo because there was a race that required pick-up trucks and there currently weren't any available for purchase.
The driving in Forza 4 feels just a bit crisper in that hard-to-describe way. Chatting about it with a friend who participates in real-life Autocross, he described his favorite aspect: "Once you get used to the car's setup, it's a lot easier to feel when oversteer and understeer are starting to set in." This sensation is crucial for a driver, especially for moments like that last corner on Laguna Seca where a bit of oversteer could send a car far enough into the gravel to make first place a distant dream. Forza developer Turn 10 has made tire simulation their bread-and-butter in the racing world, and it's obvious in every sort of corner featured in the game.
Unfortunately, that tire simulation may be part of what's holding Forza back just a little bit. In simulating that tire-to-track interaction so faithfully, the game suffers in variety. Every track is all asphalt all the time. Except that one cobblestone track. But every track is dry tires on dry streets. There is no rain, no snow, and even more sadly, no dirt. Maybe this is all coming in Forza 5, and honestly it's more of a nitpick because the tracks in the game are already so much fun to drive on that it shouldn't matter.

Forza has always been one of Microsoft's flagship series, and rightfully so when it comes to the online elements. Forza is an example of doing just about everything right on Xbox Live. You can race against your friends' ghosts or against live players. You can sell your hard work on the Forza auction house in the form of tuning setups, custom paint jobs, and even in-game photographs. About the only thing you can't do is put 14 LCDs and an Xbox in your car so that you can play Forza Motorsport while you play Forza Motorsport.
Even Forza's pay-to-play aspect is well implemented. Tokens are available for purchase on Xbox Live that can be used to acquire some of the more expensive cars. At the same time, it's ridiculously easy to accumulate credits just playing the game. The tokens are really just there for fans who want to drive that Lamborghini Reventon right away and don't have the time to save up for it. In the menus, they're present but never in the way. There aren't any extra menus devoted to tokens, and they're never presented as something meant to give the player an advantage.
Iterative games are always hard to judge. Is there enough new to make it worthwhile for casual fans? Forza 4's answer to that are the Autovista and Rival modes.

Autovista is, in short, car porn. Turn 10 shows off the 360's graphical capabilities and their own detailed renderings by letting you get much closer to your dream car than any Ferrari or Bugatti dealer would ever let you. Top Gear host Jeremy Clarkson even describes each of the cars available in the mode, giving some insight into what makes each car good, bad, or just plain remarkable. And while it's not often that visuals are worth mentioning anymore, it is clear Turn 10 has gone all-out. From the wood-grain of the Aero SuperSport or the brushed aluminum of the Ford GT to the detailed stitching in the Lamborghini Reventon, the incredible textures and attention to detail are literally jaw-dropping. The first time I saw the Reventon in Autovista, my mouth hung open as if I'd just seen it in real life. Indeed, Autovista mode is as close as you'll ever get to being a telekinetic disembodied head with a penchant for supercars.
Finally, the Rival mode: my personal favorite addition to the game. Various modes and restrictions offer a variety of ways to compete against both friends and random players. Autocross and Drift modes give amateur racing fans a way to participate in some of the more expensive hobbies out there. Better yet, playing in this mode affects your single-player. Beating a particularly challenging ghost driver will rake in credits and all those laps go toward increasing driver level and brand affinity level. The best of single-player and multi-player worlds, together at last.
Every time a new racing game comes out, I wonder what else is left to do in the world of car-driving, but somehow Turn 10 manages to make each new Forza Motorsport title feel fresh and exciting. Forza 4 is no different and worth checking out for racing fans of just about any level.