tell you now this is a fairly long review - enjoy :)
starting at the start (Prophecies):-
the game which can first is really a must for GuildWars players as the other games feature references to it and this will prove confusing to players who have not ventured through the lush and beautifully designed lands of Tyria (prophecies continent)
the game is well made with a quality storyline and hundreds of side-quests which either impact upon the storyline or give a further backing to the lore of the storyline...
the professions of the available characters vary nicly from healers (monk) - warriors - rangers - necromancers (cursers / undead masters) - mesmer (masters of illusion) - elementalists (harnace the power of the elements) - there is something here for everybody...all have advantages and weaknesses compared to others...but when played well can all beat the variety of monsters featured around the game world...
Factions: (first add on)
added two new professions (assasin (dagger using combo masters) and ritualists(spirit summoners, who can also do good damage) - these two professions are available to Faction players as well as the 6 generic professions from Prophecies!
the scenery is still great with 4 distinct zones (starter area - city - jade sea - forest)!
gameplay is a bit shorter than Prophecies but still providing long play tme with hundreds of additional quests...
Nightfall (second expansion)
two more professions added (dervish - scythe wielder, similar to warrior but with less armor but more damage) and paragons (spear users with immense damage and incredible party-wide armor buffs)
the game has good gameplay again with different zones of scenery, from lush areas to baron wastelands! well designed and crafted for maximum enjoyment!
the biggest add-on however in NightFall compared to Factions and Prophecies is the option to add heroes to your party (instead of the henchmen available in Factions and Prophecies) these act as allys similar to henchmen but you can customise their weapon sets as well as attribute points and skills - for additional support in battle!
all of these games have 1000s of skills to choose from for perfect mix and match options...
millions of players so you can party up with other people if you wish too!
many other things as well...
hope you found this review of some help when it comes to picking this great MMORPG...hope you enjoy your purchase :)