Most of the time its generic responses, the rarely even read the reports

There can only be one "The Best" so Good will have to do.

I've never had anything resolved in less than two emails so I'm rating them as bad.

I won't say the worst because I deal with companies like TWC.

I have only had a couple of issues. They have always responded both quickly and fairly in each case so... no complaints.

Not usually very helpful. Get a lot of "copy/paste" replies and generic fixes that have nothing to do with the issue at hand.

Some of which include;
1.) Make sure you're connected to the Internet.
2.) Did you reset your router?
3.) Flush toilet and wiggle handle.
4.) Remove all addons.
5.) Repair your client.
6.) I'm sorry be we cannot be of any help at this time. Please contact your ISP for further support.

The majority of my tickets get closed with a clearly canned response that shows they did not even read the ticket. Its frustrating that I have to reopen tickets that were obviously ignored.

In about 100 reports in 2 years, I got 1 useful productive interaction.
Everything else is completely generic useless answers as others stated.

I want to say bad...

I have issues with them treating people with the same issues differently. Multiple people can decon or delete items and be told there is nothing that can be done(and rightly so), but then someone else will do it and post a praise ZOS thread about them restoring their item. That is just wrong IMO, as customers we should all receive the same treatment.

Some of the generic responses are often insulting to players. You report someone for cheating/exploits and get told to put the player on ignore.

One ticket I had, I fully explained my problem. The response was them telling me to do what I already told them I could not do, with an explanation of why I couldn't do it. This went back and forth them continually telling me to do, what I tried to do and couldn't, 3 times before I stopped replying and thus the ticket was closed. The issue became moot a week later when TG was released.

Then there are the bug/issues you send in and you know it's not something they need to respond to, it's not something that can just be quick fixed. Things that affect many players... And they send you a mail 1-2 weeks later telling you sorry they didn't meet your expectations or some crap. Meanwhile the issue has since been resolved. Some tickets don't need a response, don't send one... Especially not weeks later.

But...

The few times I have had serious issues that were fixable... The response time was lightening fast. I mean literally less than 10 minutes on one issue where my regen got stuck on 0 after completing a quest.

So maybe it's about which support agent you get, what mood they are in, and how you treat them in your correspondence. Or maybe it's about priority.

ESO has Customer Support?

Sarcasm aside, an email only response system leaves much to be desired. Even worse, every ticket comes with an automated response that requres further input from the complainant to even hope for resolution. This is the WORST support I've ever seen.

I seriously have had great luck with customer support! One of my tickets was about pvp and they said they were referring me to somebody else. That person answered me and said he also plays pvp on Xbox and we had quite a long discussion about the state of pvp and what they are working on to improve it.

There is a customer support?

The last three tickets I sent in have been ignored. No answer at all.