Blockbuster Online lists all available editions of titles on their Web site, so that you can choose between widescreen, pan & scan, or special editions. Some are available to rent online and purchase, while others are available for purchase only or in their bricks and mortar stores only. Two Brothers is one such movie. Only the pan & scan version is available for online rentals.
Netflix doesn't give you a choice of editions (yet), but they do offer the widescreen version (my preferred format) for online rental.