Skipping the usual 'America was late' stuff I'm going to shamelessly reference wikipedia because it's accessible and so I don't look biased.
I'm also assuming that we're using a 'western oriented, freedom loving, human rights respecting' view of good, and the opposite for evil. I'm not going to start on about whether good and evil are subjective, or if the ancient Romans, Galactic Empire, Mordor or *insert different culture here* would agree.
The axis were evil, and stopping them was obviously a good thing. Stalin wasn't that [http://en.wikipedia.org/wiki/Great_Purge] nice [http://en.wikipedia.org/wiki/Holodomor] though (he was probably responsible for more deaths that Hitler), and we were allied with him, and did a pretty good job of whitewashing [http://en.wikipedia.org/wiki/British_propaganda_during_World_War_II#Soviet_Union] his various unpleasantries.
The western allies did some pretty morally dubious things as well. Tokyo, Hamburg and Dresden firebombings come to mind. These were arguably a necessary evil, but targeting civilians for the purposes of terror can never be considered 'good' per se.
The fact that we allowed plenty of people who were clear war criminals escape conviction [http://en.wikipedia.org/wiki/Operation_Paperclip] out of convenience was not an act of good versus evil (Ex-Nazi scientists basically sorted out both the US and Soviet space programs). Similarly the lack of war crimes convictions against the Japanese is pretty astounding. Though we gained [http://en.wikipedia.org/wiki/Unit_731] something there too. In fact, most of the postwar actions of all of the allies can be seen as a case of trying to consolidate their own power, not necessarily trying to do good or bring justice. The carving up of Europe between East and West speaks volumes about this. Even the fact that the big five have a veto at the UN was so that the allies could retain a degree of power over a changing world.
So World War 2 was a necessary fight against a very real evil, but the Allies were absolutely willing to do fairly nasty things to further their own ends (not generally 'for the good of mankind' either). The Soviet side of the alliance could in no way be described as 'good' at all! There is however, no doubt, that the world was in better shape in 1950 than it would have been if the Axis had won in 1945.
On to the cold war. This one is much less clear cut. The Soviet and Chinese governments were dictatorships with little regard for freedom of speech or human rights. This is obviously bad, so one instinctively sides with the West. But if you look a bit deeper, we've been guilty of some startling hypocrisies as well.
There are multiple instances [http://en.wikipedia.org/wiki/Covert_U.S._regime_change_actions#During_the_Cold_War] during the Cold War when the West installed puppet dictatorships to try to prevent the spread of communism. In a lot of instances, these dictatorships were far more brutal and repressive than the communist governments they were supposed to stop. The USA had a particular habit of using the CIA to covertly fund rebel organisations in order to hinder communist governments. In a couple of instances, DEMOCRATICALLY ELECTED governments were overthrown because they were seen as too left wing (or even because the democratic government in question traded with a communist power instead of with US companies). Overthrowing a democratic government is not a 'good' act on whatever grounds.
Aside from that, it makes for a supremely stupid statement: "Yeah, we removed their right to vote in the name of democracy. We paid for a dictator to imprison, torture and kill them in the name of freedom"
*** [Aside: In the later Cold wWr, and to this day, American intervention tended to be economic, but produces similar effects. There are plenty of instances of American companies promoting human rights abuses [http://en.wikipedia.org/wiki/ExxonMobil_violations_in_Indonesia] in order to make things easier for themselves. The US government can tend to turn a blind eye [http://en.wikipedia.org/wiki/ExxonMobil#Foreign_business_practices] to this kind of thing when they have economic interests in the regions. This isn't the action of a 'good' side. /Aside]***
Of course, it wasn't just the Americans. We in the UK were up to our eyes in it as well. Trying to gain a measure of economic control over the remnants of the British Empire led to some pretty [http://en.wikipedia.org/wiki/1953_Iranian_coup_d%27%C3%A9tat] disgusting [en.wikipedia.org/wiki/Mau_Mau_Uprising] things. The attempt to play god with Palestine and what would become the Pakistan-India border area means that ethnic tension exists to this day. We were egged on by the US because they preferred Colonialism to Communism.
The other colonial powers did much the same, and in a fair number of instances were worse than the UK.
And that's just foreign policy. Let's not forget that the US in the 1950's was hardly a utopia worthy of export. McCarthyism [http://en.wikipedia.org/wiki/McCarthyism] was rampant, anyone thought to be even slightly left wing was mercilessly harassed by borderline vigilantes and law enforcement agencies. Literally thousands [http://en.wikipedia.org/wiki/McCarthyism#Victims_of_McCarthyism] of people were fired from jobs or imprisoned, many on very tenuous grounds and with no legal recourse. Even being found to be gay or a civil rights activist could result in a person being labelled subversive, and therefore a communist. Even if not strictly against the letter of the Constitution, it still represented a radical departure from the spirit of democracy and freedom of speech.
Concurrent with this, the US fought wars in Korea and Vietnam, ostensibly for freedom and fairness, while black people [http://en.wikipedia.org/wiki/African-Americans_in_the_United_States_military_before_desegregation] were denied equal rights at home. Black servicemen died for rights that they themselves did not have. (This extends all the way back to WW2 and before)
I'm not saying that the communist states were any better, they usually weren't. But they at least tried to make other countries have the same system as what they had domestically, however misguided it was. Whereas the West all to often did its level best to persuade the world that they were acting for the common good, when it was purely anti-communist sentiment motivating them. Intervention from a flawed superpower led to far greater harm coming to a multitude of smaller countries that were unlucky enough to be used in proxy wars for the most tenuous of reasons. It's not so much a case of 'good versus evil' or even 'evil versus evil'.
It was just a bloody mess.
***EDIT: I've just thought that I've said In my first line that I don't want to be biased, and then talked almost exclusively about the West being horrible. This isn't because I think, or want to imply that the West was altogether worse than Communism. It's clear that if the communists had 'won' we'd have no democracy, which would have been a decidedly BAD outcome!
It's just that everyone already hears about how terrible communism was, so I thought I'd talk primarily about the abuses committed by the Western world, that you tend not hear about so much.
I was going to talk about both originally, but figured I've made quite a wall of text anyway, and it really doesn't need to be twice as long! ***
