Alright, so i was playing jungle amumu, and my bot lane and top lane were losing horribly, so i had to gank constantly. Oh, and the lanes were losing by themselves, not because of pressure from their jungle. So after laning phase is over, i have about 86 cs, and their jungle has about 140 (jungle shyvana btw). Now, their jungler starts bashing on me about it and saying "you ganked too much" "You're a horrible jungler" "Look up a guide" Etc. I told him that he only had more cs because he only had to gank mid a couple times but he just kept saying "Yea, you gank too much". So i was wondering, what defines a good jungler, creep score, ganks, or something i havent even mentioned?

Depends on the Jungler.

You have to realize their are diffrent types of Junglers.

Ganking Junglers: Focus on Ganking and Killing Lanes, usually fall off if no successful ganks (Alistar and Fizz go here).
Farming Junglers: Farm, Farm, Farm, Farm unless a lane is severely out of position never stop killing the creep. (Master Yi and Gangplank go here)
Control Junglers: Invade the enemy, decimate their camps or Alternetivly find them and kill them. (Trundle and Nunu go here).

So Junglers can be Hybridized as well.

For instance

Shaco: Ganking/Control Jungler.
Shyvana: Farming/Control Jungler.
Skarner: Ganking/Farming Jungler.

Also Farmer beats Ganker, Ganker beats Controller, Controller beats Farmer.

Amumu is primarily a ganker, and should expect to have less CS then junglers who are more concentrated on farming (Like Shyvana) the trade off is that you have much more potent ganks, and should be up in kills. If you ganked a bunch and had no kills you are either a TERRIBLE jungler (this is unlikely, do to the inherent power of nunu's Bandage toss for ganks) or your lanes dont know how to properly "prep" a gank (this is far more likely as most laners have never jungled themselves and dont realize its a complete waste of time to gank lanes that are at full health, or ones where you ally has less then 2 bars do to the fact that they are getting destroyed in lane).

It depends on your team as much as it does on your champion too. Even if you're playing a jungler who's not known as a strong ganker, if you're with a pre-made, simply having a 3v2 or 2v1 situation can be enough for the gank to succeed if you're all on the same page and communicating.

Some junglers can start ganking at level 1 or 2 and mostly get fed off of assists. Other junglers want to farm as hard and as fast as they can to hit level 6. Plus, you have to balance the needs of your team. If top is wholly unable to hold his lane, is it better to baby sit him and have you fall behind, or is it better to leave top to fend for himself and have to deal with a fed enemy? In that light, a good jungler is one who's able to process a ton of ever changing information and react to it quickly in a way that most benefits the team as a whole.

The primary job of a jungler is to maintain map control. This means buffs, dragon, baron, and lanes. I don't really care how you do it, though your laners might.

"What defines a good jungler"

A jungler who is playing to win the game.

If one of your lanes is struggling, you should look to lend them aid. Some lanes can't be helped though and it's always your call on whether it's worth you traveling to a far off lane to try to gank. Keep in mind that any time you gank for a lane that is an investment of your time. If it doesn't pay off for your laner or you then is was a bad investment usually.

If lanes are pushed you can do one of two things. Farm your jungle or force an objective. When your team has a lane pushed, that means that the enemy has to spend the next 30 seconds or so absorbing the farm at the turret before they can react to anything you are trying to do. Dragon is a good straight forward objective for you to take and is a good way to build a lead. Another form of objective is to take towers. Your bottom lane is pushed and dragon isn't up? Can you force them off their tower or dive them easily? Maybe you should call for your bottom lane to cut up through their jungle and 4v1 mid to take THAT tower.

Being the jungler means that you have the potential to influence the whole map. A good jungler will be able to gank and snowball lanes. A great jungler will be able to invest his time and energy getting things done where they need to be done and ultimately win the game for their team.

Trying to get into jungling myself, and its easily seaming to be the most complex role. You have to consider all 3 lanes, and your enemy jungle/ your own, so basically that's 5 lanes at once that your job to manage, and decide when/ where is the best place to be at that time.

Time on failed ganks puts you behind. Success can be measured if at the very least you and your lane lived, but you forced the enemy back to base, but of course good for your lane, still bad for your own gold, at least that enemy won't be as farmed as they could have been to kill you later as easily.

Some junlgers are naturally going to have less minon kills, not every one who jungles is amazing at camp clearing with a single skill. I believe it was said pretty good by that EzraTwitch.

Ganker junglers like blitzcrank /alistar for example, have pretty poor clear times, but their power to secure kills in a gank is top notch. As such should be ganking as soon as lvl 2 or 3. They farm players not the jungle. Thats how those type of champions jungle well. If they fail a few too many attempts though, they'll be pretty behind for gold and suck and die later on. But if you get a few kills for your team out of it, those lanes will far pretty far behind your own lanes.

This is 100% wrong. League of Legends ain't rock paper scissors, bud.

Farming loses to ganking if the ganker puts himself and his team farther ahead than the farmer. Ganking loses to counterjungling if the ganker can't turn out a successful gank. Counterjungling loses to farming if you get counter-counter jungled because the jungle and mid see you invade via a ward. And vice versa, a farmer can beat a ganker and a ganker can beat a counter-jungler and a counter-jungler can beat a farmer.

Jungling is not a glorified game of rock paper scissors.

Its not a 100% insta loose or win, its it how ever, seen as the standard pick/ counter pick types, where they'll have a disadvantage or advantage against other types of junglers, under ideal circumstances.

Are we going on Rock, Paper, Scissors, SHOOT! Or Rock, Paper, SCISSORS!

That was actually mostly right. Generally, an average ganker will lose to an average farmer if the lanes play competently. But the average farmer if he doesn't have good control can get pretty screwed by counter-jungling.

However, very few champs fit 100% in any one catagory only. What he stated is an abstraction to make it easier to discuss something that is complicated. It is not a hard rule. So it really isn't exactly rock paper scissors.