This is very debatable, it totally depends on what you're looking for. What on earth is the "best".
London is the best in my opinion because I get the best latency to it (not surprising - I live < 50 miles) and its had 0 outages since I've been in it.
They're all equally reliable in my opinion, Fremont just got unlucky. Every DC is going likely to experience some form of major outage throughout its lifetime. If you're running anything serious you should have redundancy in another DC so it doesn't matter if your primary fails anyhow (your primary will fail - don't ever assume it won't just because you picked a "good" DC).
My situation is a bit different. I'm in Australia. It differs as follows:
I chose Fremont in the past because it's the lowest latency to me.
Now, however, I have a website that I want to place in a separate data center from Fremont. All the other data centers in North America are about the same latency to me. So latency doesn't really enter into the equation _for_my_this_particular_case_. I figured I'd just choose a data center based on perceived reliability, and perhaps proximity to the 'center of gravity' of the Internet (whereever that is).
But ...
I wanted to make the poll general so it's more useful for future readers. Hence the resultant wording.
It's really a toss-up. Dallas is the second-closest, obviously. London might give you a westward route across Eurasia instead of eastward through the US. I think I'd probably do Newark or London, avoiding Dallas in case most of North America falls into the ocean, and avoiding Atlanta in case something changes with the port blocking.
London is the best in my opinion because I get the best latency to it (not surprising - I live < 50 miles) and its had 0 outages since I've been in it.
They're all equally reliable in my opinion, Fremont just got unlucky. Every DC is going likely to experience some form of major outage throughout its lifetime. If you're running anything serious you should have redundancy in another DC so it doesn't matter if your primary fails anyhow (your primary will fail - don't ever assume it won't just because you picked a "good" DC).