Forza Horizon is my favorite Forza to date for a few reasons. Often times, in forza 4, many people who didn't tune their cars correctly/ have good set ups didn't stand much of a chance at all. This isn't the case at all in forza horizon. While some veterans don't like how tuning isn't in this forza, it really is a benefit for the rest of us. For people who really don't know what tire pressure works best for their car, it makes the competition more fair. In many cases, you can use the default car they give you and reach a high spot. Another feeling in forza 4 that is gone in forza horizon was the feeling that one small touch from another car would put you in last place. Surviving the first turn was almost always my first priority when going into a race. This is gone in forza horizon, while you can't stop crashers, the cars are much less sensative to other cars, which overall makes fighting for first place even more fun.
When it comes to single player , it is much more engaging than the previous forza games. Instead of going down a list or calendar you are doing races and beating rivals in order to get to the next wristband. Despite these rivals being a little bit cliche, it makes the game a whole lot more fun. Forza Horizon is a game you can play for hours and hours with free roam/single player/ multiplayer, not to mention the amazing detail in each and every car. I personally think it's definitely worth a buy, but if you can't just try to rent it, even if you haven't been to happy/successful in the previous forza games.
This game is near perfect racing experience that takes the quality you have come to expect from the Forza series and mixes in some street racing elements. If you loved previous Forza you are sure to like this. What's nice is that it breaks from the confines of the standard racing simulation that it has mastered and gives you a new arena to take off into, while using that fabulous engine.
The sim aspects are refined and simplified for this game which works out well because this game is more of an open world racing game than a simulation. There is constantly something new and interesting to do within the beautiful Colorado landscape. So you'll spend very little time rifling through menus and more time diving into races, challenges, stunts and time based challenges. Just roll with it. The game is deep and fun and a nice change of pace from the standard Forza sim. It also avoids being over the top like many of the Need for Speed games and its brethren. It seems like the game runs at 30fps which some may scoff at but when you see how smooth it runs and how the frame rate never buckles you'll see why.
Also, if you have played previous Forza games and have a save file in your system you get gifted a bunch of cars when you start the game which is always nice. This is also a keeper because of its depth, a rental is not enough.
Being a big Forza fan i was worried that this game wouldn't live up to the name. Although this game is open world it still feels great. Its a little more arcade-ish than i would've liked, but all in all this is still a really fun and really addictive game.
The cars look amazing and the scenery is a nice change of pace from racetracks. the only reason I didn't give it a 10 was because of the loss of realism in the physics.