DPS isn't king, total damage done before dying is king. And in that measure, Vaporeon kicks the other eeveeloutions to the curb.
Further, typing isn't about which is better, but about which fits the attack you're making. Going up against Rhydon or eventually Groudon, water is way more important than electric. What matters is the best attacker of any given type. Vaporeon remains the best overall water attacker, better than Gyarados (no water quick move), Suicune (do I even need to explain that?) Lugia (no STAB, no quick move), and any others. Jolteon is behind Zapdos/Raichu, Flareon is behind Moltres/Entei, and Espeon is behind Mewtwo, but no one is beating Vaporeon until Kyogre is available, or they make some major changes. And that's why Vaporeon is the most important Eeveelution.
Why is Vaporeon still considered the best Eeveelution?
Jolteon, Flareon and Espeon all have higher DPS, in a meta where DPS is king. Yes, Vaporeon survives longer, but like I said, DPS is king in the current meta. As for typing, electric is definitely more important than water, psychic is about equal with water.
So, Vaporeon should be equal with Jolteon and Espeon, and a little better than Flareon. Not that much better.
Answers
DPS is usually king because anchors exist. Think about the fact that most people that solo Alakazam/Gengar usually open with glassier Pokemon like Alakazam, Gengar, and Mewtwo instead of using solely pokemon like Tyranitar or Lugia. Same with using Espeon/Alakazam against Machamp instead of solely Lugia.
That being said, I agree. All of the other current Eeveelutions (aside from Umbreon with no real place to begin with) can be easily outdone by legendaries. Suicune's only edge against Vaporeon is potion efficiency and that's no real boon with potions added to raids.
Because it’s the only one to not be surpassed by something else of the same type so far.
Jolteon has Zapdos and Raikou as competition. Flareon has Moltres and Entei. Espeon is still very relevant unless one has a Mewtwo (I do not.). There’s nothing else on the horizon to challenge Vaporeon as the best all round water attacker, at least until we get the Gen 3 legendary Kyogre.
I think Vaporeon continues to endure because it's still the best water type around. Gyarados lacks a water-type quick move and nothing else boasts Vaporeon's overall stats. On the other hand, Jolteon and Flareon are outclassed by the legendary birds and beasts of their respective types, and Espeon is about on par with Alakazam (to say nothing of Mewtwo). Comparatively speaking, Vaporeon is the best in its niche. I would say that Espeon ranks second, with Jolteon and Flareon trailing behind (although still respectable choices in certain situations).
well i dunno who exactly you cite as considering vapes the best but i'd have to agree - you are right that dps is #1 concern and always has and will be but you need to consider both type and real world applications. very dependent on what you are fighting ofc, i'm assuming you mean gyms.
send a jolteon or flareon against any top tier poke - the jolt will destroy a gyrados (who puts them in gyms anymore...) but neither have any super effectiveness against common defenders nor any resistances worth noting other than fire vs. fairy and their hp is low enough that quick attacks will mount up and a charge move is major trouble if not dodged. umbreon is too low cp but espeons are good in the current meta as they are high dmg, rarely resisted and have ok survival/resistance against very common psychic attacks, even if their best moves are slow so makes for tough dodging.
vapes have a very spammy fast move with high dps and 2/3 of their charge moves are very fast too so are great dodgers, have near twice the hp of other eevees, and it's very rare you'll see a defender that resists or super effective's them - they are cheap, common and versatile.
Vaporeon has awesome charge moves but Water Gun is a pretty poor quick move in terms of damage. It has decent energy but not enough to pull it out of being mediocre. It's comparable to Bite, which is outclassed in energy by Snarl and damage by Feint Attack. There's just no better Water quick move available yet. (Hidden Power is identical but half the speed and double everything else)
It's crazy because Vaporeon, a Pokemon now with stats that bring its CP over 3000 (and is too easy to obtain, might I add), used to be below 3000 CP before the major CP balance came about last year, and even then, Vaporeon was still pretty good. Vaporeon's pre-buff last year would definitely be either on par or better than Suicune by a very slight margin as the best current water Pokemon in the game, and would have been equal with current Jolteon, Espeon, and Flareon.
I would have preferred Niantic leaving Vaporeon untouched or just lowering her stats slightly for the sake of balance. Why she was buffed up this much is beyond me, though. Suicune should naturally be the better water type. If Niantic can nerf Pokemon like Mewtwo and Ho-oh, they can definitely buff a Pokemon like Suicune.
i'd love to see them get bubble (or even something normal typed) for both attack and defence, watergun is indeed terrible and it's one of the very few high cp monsters without an option between quick and slow here. i have a dozen i used to use as primary defenders but i rarely use them anymore other than attacking rhydon/golem and on ttar/fire 'mon raids, mostly for their survival. make no mistake their charge moves are deadly attack or defence, with water pulse being the only letdown as it's easy to dodge.