No Troy, his victory did not bring China into the war directly it was his belligerant posturing and posting troops too close to the Yalu that brought China into the war. This showed a colossal misjudgement of the strategic situation. Not very indicative of a Great General if you ask me. His threatening of China was what tipped the scales to bring a wavering China into the war. Then he wanted to use nuclear weapons to rescue himself, the use of which would have almost certainly triggered the third world war. Gets better and better doesn't it?
Besides amphibious envelopment was not a strategy developed by MacArthur, the British had been practicing it for centuries. The U.S. Marines were far more influential in developing a coherant amphibious doctrine during the 1920's and 30's after the failed amphibious campaigns of WW1. You should also look at some of the central pacific campaigns, particularly how Nimitz isolated and neutralized the Caroline Islands and Truk in 1944. These were campaigns that were both tactically well fought as well as strategically victorious, something MacArthur can't claim. They were also fine examples of amphibious envelopments which had precisely nothing to do with MacArthur. Besides Nimitz and Holland Smith achieved these victories almost 10 years before MacArthur launched the Inchon landings.
If you would like to see some innovative Generals during the Second World War who acually invented new methods of warfare I can suggest a number of places to look before MacArthur. I already mentioned Nimitz, admittedly an Admiral not a General, during the Central Pacific Campaign. You should also look at Field Marshal Slim during the Burmese Campaign. Slim fought a very successful and innovative jungle campaign against the Japanese. He invented tactics and strategies that not only led him to victory but influenced Generals as diverse as Vo Nguyen Giap and Creighton Abrams.
You should also examine Heinz Guderian as the inventor of Blitzkrieg and practicioner of it in some of the most successful campaigns of the war. They included, Poland in 1939 France in 1940, Barbarossa in 1941. In addition he fought under far more onerous directions from Hitler than MacArthur ever did from FDR or Truman. Look at any war college syllabus I garuntee you they will have Guderian's writings and not MacArthur's. His writings were very perceptive and forward looking. I could go on for the Second World War, but you should really be getting the point by now.