Quote from pavilionaire >>

How can this question be answered? It's a game for parties, not single PCs, and the best party probably has more than one class. In that case we can't say that any one of those classes is better than the other, because they each complement each other.

Then, should we answer according to what class is the best if you have a party of all one class?

I feel like we want to go magic user. There are some obstacles that pretty much require magic to solve, but obstacles that can be solved by brute force can usually be solved in another way by the use of magic.

Wizards are too squishy and would probably get wrecked, at least at low level. Anyway, you probably need someone with healing.

Cleric. It's probably cleric. One of the domains that gets heavy armor proficiency so you can be tanky. Clerics do pretty amazing on offense too. Guiding Bolt is pretty strong damage, and if you just stand in a circle throwing Guiding Bolts, you're all going to have advantage. But it's the multi-round duration spells that really shine. Spirit Guardians is potentially damaging every enemy that's fighting you in melee once per party member each round. And you can have Spiritual Weapon and Guardian of Faith up at the same time, since they're not concentration.

Probably Nature Cleric. That gives you some exploration skills and access to a variety of damage type options other than radiant.

 I actually think that this dude is right. Let me edit my question: what is the best COMBINATION of classes?