Keep it simple
GW1's attributes and skillbar is a robust, simple system. 8 skills is just enough to squeeze in a good combo and some utility skills, and the attribute points work well too. It would be stupid to carry all the skills you own into battle, and to max out all attributes as you level up. Save that for Oblivion - Guild Wars is about striking the perfect balance of skills+attributes to make your build most efficient.
Similar to the note on my GW1 suggestions page, I just want to quickly mention that the right amount of skills for a profession is: Enough that you can fill a skillbar with useful spells of any single attribute, and there is a useful elite for any build in this way. Using ritualists as an example, I should be able to fill my skillbar with a single ashes spell, and 7 resto skills that synergize with holding items. The same goes for weapon spells, spirit-related spells, etc. This will obviously not necessarily happen, having a full skillbar of a single type of skill, but it's useful to have more variety so you can adjust according to the situation.
While hanging around in the guild hall on my male Ele, dancing my little dork dance, a friend commented that I should get some dance lessons. We laughed, but it got me to thinking - maybe certain quests or an NPC could allow a player to change the style of emotes that he uses. Don't like that lame dance? Go purchase Dance Lessons from the local town square, for 1plat. Want to look more manly in your actions? Pick up the "Not Buff Enough" quest, and change your character's animations for various emotes. Would add some interesting customization to people's characters. I figure if each race uses the same skeleton, one for each gender, why not? Most professions in GW1 share certain emotes, like female monk + warrior have the same /sit, etc. Perhaps in an effort to increase RP value, the user could customize his own emotes.
Lore in general
Flesh it out. Guildwars has a fairly unique bunch of races, lore, etc. and it's worth fleshing out to make it a rich environment. I want to be able to talk to a historian and find out what's happened in the last 500 years.
Powerful Skills should feel powerful
Spells like Meteor Shower with a 5 second cast don't really feel very powerful considering their stats. I'd like for GW2 to make an effort to produce spells and abilities that make the user look and feel powerful. The spammable spells such as Flare should be maybe 1/2 second cast with no cooldown, so you can spam them DBZ-style, with new animations (alternating hands for each cast). Obviously balance is important in both PvE and PvP, but this issue is mainly aesthetic. It'd be cool to see, as my ele summons 5 seconds' worth of power to cast Meteor Shower, flames and rocks floating around my character. The big, powerful spells should have additional, extravagant effects to show how serious a spell is. The little, quick spells like Flare, Orison of Healing, etc. only need a simple animation and effect, where the hugely powerful spells should get additional effects to show that you mean business.