This might even be the definitive open-world experience. Rockstar has created a game that fulfills nearly every promise that GTA IV brought to the table, and it raises the bar for "sandbox" games in terms of both graphics and gameplay.
Red Dead Redemption nails every aspect of what a "Wild West" game should be. The game has shootouts, cacti, trains, horses, everything you would expect. There's almost nowhere to go after this, as every expectation I have of a "western" game has been met. It truly does feel like you've got a major part in an old spaghetti western.
The gameplay is very remeniscent of GTA IV, though it's obvious that Rockstar has learned some lessons from their previous game. You are always free to do what you want to do, and there are never any characters calling you to go bowling. There are a variety of past times, including poker, horseshoes, and "five-finger fillet", but you're never compelled to play them if you don't want to. You can also hunt and skin animals, help random strangers, or try to take down hostile gangs. Your actions affect your "honor" and "fame", which give consequence to your actions but never feel intrusive.
The gunplay is smooth, and the bullet-time-style "dead eye" feature allows you to paint multiple targets to (hopefully) take them all out at once. The game has the standard cover and health-regeneration systems, meaning that everything works like you would expect with few surprises.
Horse riding takes getting used to, but it soon proves to be much more engaging than driving cars because you become more attached to your "vehicle", and you begin to find a rhythm to your acceleration that keeps you at a gallop while maintaining your horse's stamina. You can shoot while riding your horse, and if yours gets shot you can break a wild horse or but a deed for one from one of the general stores in the great-looking towns scattered throughout the impressively large play area.
The only major flaw with the game is that it works so hard to establish a mood, only to have the mood broken by frequent bugs and glitches. They very rarely affect gameplay, but they break the immersion that is one of the game's greatest strengths. Ultimately though, they can't detract from the quality of the game, which will surely be remembered as one of the best open-world games of all time. It will also more than likely be used as "inspiration" for many future games, just like GTA before it.