This site has a pretty good list of the minor changes from year to year.

Quote from the website, "The most extensive and detailed Toyota 4Runner historical chronological archives on the web. Year by year changes, specifications, information, photographs, color charts and more."

Just ran across this thread as I'm in the market for a used 5th Gen. How is this, for anyone else still wondering? This breaks down the differences from year to year, as well as trim packages...
Toyota 4Runner Models, Generations & Redesigns | Cars.com

Old Post but may help someone else so..

In 2012 they made a small engine/horsepower tweak, which added ~15HP I believe and it also effected the MPGs, the highway mileage went from 22 to 20 city remained undefeated.

With the 2014 facelift came a whole new face for the SR5 and trail models (which would carry over to all otherlater models except the Limited and the newer TRD Sport). The new face came with a front bumper that was 2 inches higher allowing more ground clearance for offroading. With that they also went and removed the side skirts which also gave the side 2 more inches of clearance and the rear bumper was also replaced with a 2 inch shorter one. The door handles were also replaced except not the Limited and later introduced TRD Sport remain with the old handles that came on the 2010-2013 models. The outside side mirror assembly was replaced with ones that could accommodate the mirrors from the Rav4 and Tacoma of similar year. Limited models remained with the same height bumpers as the 2010-2013 models. The only difference that came for the facelifted 2014+ Limited models was they got a newer face still with all the chrome features the earlier models had and the new headlight assembly too.