A little revisionist history on your part.
Early in the War, McClellan played an important role in raising a well-trained and organized army for the Union. However, meticulous in his planning and preparations, his leadership skills during battles were questioned, and he was accused of being incompetent and overly cautious. While skilled in organization, he lacked the decisive drive of Robert E. Lee, Ulysses S. Grant, or William Tecumseh Sherman, who were willing to risk a major battle even when all preparations were not perfect. The failure of his Peninsula Campaign in 1862 to seize Richmond was due in no small part to McClellan's slow and cautious troop movements toward the Confederate capital of Richmond, which provided the Confederate leaders valuable time to strengthen the city's defenses.
General McClellan also seemed never to grasp that he needed to maintain the trust of U.S. President Abraham Lincoln, and proved to be frustratingly insubordinate to the commander-in-chief. After he was relieved of command, McClellan became the unsuccessful Democratic nominee opposing Lincoln in the 1864 presidential election.
Rummy, on the other hand, is being credited with tearing down much of the military (the Navy, for instance, must draw down by 80,000 sailors by 2009). The future Rummy military is going to rely on UAVs to do much of the USAF's airwarfare, DDX warships with only 80 sailors, an Army that uses robotic soldiers, etc.
The DOD budget, aside from the Iraq war, has gone up every year under Rumsfeld after the disasterous gutting of the military under Clinton/Cohen and the so-called peace dividend. Manning levels have also increased. As usual, you have your "facts" wrong. Who is doing the "crediting?" You and the Dems?
In addition, McClellan is responsible for the most costly blunder in US millitary history by not overrunning Lee's forces at Antietam. He withdrew waiting for a moment that would never come. The confederacy lasted three more years and costs 10s of thousands of more Union lives.