Warrior, Ranger, or Elementalist?
Warrior and Elementalist is ‘meta’ in every single game-mode (much like Guardian) which can be beneficial. Rangers tend to fall just outside of the meta, but can be relatively effective and fun nonetheless.
Warrior:
PvE; Very self-sufficient (Fury/Might/Vul-wise) making them very good solo and each group will want 1 Warrior due to Banner of Strength and Banner of Discipline.
sPvP; Warriors are great teamfighters and can hold a node relatively well on their own in any build. Providing a long-lasting Firefield with a few Blast-Finishers to provide Might for the group and good passive survivability. Rez/Stomp control is decent.
WvW; Multiple succesful Roaming Builds. Any Zerg will want multiple Warriors due to their amazing CC making the live of anyone not having Stability hell.
Elementalist:
PvE; Also very self-sufficient, easily providing permanent Fury, decent Might and high damage over-all. Their survivability can be trickier at first, especially compared to a Warrior. Any team will want 1-2 Elementalist to provide Permanent Fury for the whole group. A Staff Elementalist mixed with a Scepter + LH Elementalist can maintain permanent Fury and 25 Might for a group most of the time. Glyph of Storms (Air) can cause 2 Elementalist to provide excellent Vulnerability for a considerable amount of time and Frost Bow has a 5 second stun along with good damage.
sPvP; D/D and Staff Elementalist are both rather popular. Both good teamfight and 1 v 1 potentional. Like a Warrior they are relatively defensive (though active rather than passive, so you’ll be weaker on rez/stomp control) and improve their (and the teams) damage through Might. Provides decent support through some Protection and Healing for anyone near them.
WvW; D/D is one of the most popular Roaming Specs, good survivability, damage and escapeability (especially with FGS.) Staff Elementalist tend to be present in any Zerg, providing Fire and Waterfields respectively aswell as good CC options through Earth and Air.
Over-all Elementalist tends to be a bit trickier than Warrior (often build squishier or focussed around active defenses rather than passive survivability.) They also have more skills to juggle/cooldowns to manage. In PvE overlapping fields can be difficult for people to get used to, but after some practice it’s really not that difficult. I personally feel Warrior is easier to play over-all, but Elementalist offers more once fights become familiar and my experience as an Elementalist grew, for both me and my team. (This is a personal preferance though!)
Ranger doesn’t really stand out in anything. In PvE they have Spotter and Frost Spirit to buff the groups damage along with high burst (Longbow 5→2) and decent sustain (Sword 1) which comes with the big downside that some people get nerved by Swords auto-attack chain (dodge doesn’t interrupt it.) They can be a great addition but often a second Elementalist is preferred. In sPvP they provide really good DPS in Teamfights and decent 1 v 1 potentional, but nothing to make them stand out (Thief has higher mobility, Engineer more CC, Elementalist/Warrior more utility/support, Mesmer less survivability but more utility (Portal) and some Boon-stripping, etc.) and in WvW they don’t have the support a Guardian has, the DPS a Necromancer has, the Utility an Elementalist has or the CC a Warrior has. But if you’ll enjoy Ranger, play it. Fun class and not useless by any means, just not as ideal in most cases.