Historically, the Confederates clearly won the first day. Who knows what would have happened if Ewell had tried to take Cemetary Hill. They had won the day, but were also pretty beat up.
The second day was a draw. Cemetary Hill and Culp's Hill were still in Union hands and the attempt to turn the Union left at Little Round Top had failed, possibly because the Confederates had not gone far enough to their right, or because Longstreet delayed the attack too long allowing the 20th Maine and others to conduct their heroic defense. In Longstreet's defense, have you ever tried moving that many men at a time?
The third day ended the Battle of Gettysburg in a clear Union victory. The attacks on Cemetary Hill and Culp's Hill were clearly hopeless and the charge against the Union Center on Cemetary Ridge was just plain crazy. BTW, the 20th Maine was on on the left end of the line during "Pickett's" charge and was acting as a reserve. They did not take part in that fight.
The final result of the Battle of Gettysburg was about 28,000 of the Confederate killed, wounded or captured. That was 40% of the Lee's army and a loss that could not be made up. The Union losses were about 23,000, about 26% of Meade's army. Overall, about 1/3 of the Americans who took part in that battle were killed, wounded or captured.