For me it would be pvp rewards. Get rid of having to cast a spell to pvp on a pvp server and give me some reward for actually killing someone. Either pvp points to spend on armor like Aion or pvp titles...Something!
Tera's combat system is supposed to be soo revolutionary but I liked it the first time I saw it in Asheron's Call. Too bad they didn't jack their pvp system as well: looting people, no safe zones...long live Darktide!
Different leveling system (ie no quest system)... haven't played it yet, but I hear GW2 is doing it different....
Dynamic world content like Rift.
Had it had something like that I think it would've stood out even more.
I just did the GW2 beta and the way it works is events are constantly going on around you. You get a message and you choose whether or not to participate in the "event." Granted these are just constantly occurring "quests," it was still different thus novel thus cool after 5 million mmo's wherein you just look for "!" or "?" above an npc's head, take all quests, run around looking for "x", "!" either picking things up or killing things...
I did some levelling in GW2 but I primarily just queued for battlegroundesque matches wherein they give you access to end game items and make you max level unlocking all your skills. I was shocked how much I liked it. Most people level to get endgame gear and unlock all their character's skills and here they just gave it to you. Without the hardwork getting the items I thought it would be meaningless but the gameplay was so much fun, I found it hard to go quest and level.
If you added the targeting system and look of Tera to GW2, you would have 1 hell of a game. I really was not looking forward to GW2 a huge amount but I will most likely play it more than Tera.
I will play it too... but I don't want to ruin the newness or freshness of it... so I've tried not to look too much into it. That all sounds very interesting though.
Ya Tera's combat (targeting) is the only "new" (once again Asheron's Call had this combat system eons ago jsut without the crosshair) concept I have seen thus far.
GW2 has the unique battlegrounds, no dedicated healing class, truly novel classes, no monthly fee...
It is a great direction for many reasons and boy they are different games. During the beta weekend of GW2 and the release of Tera I was switching back and forth and my nostromo hand was quite confused.