I agree with you, these a called game genres. Did you really think that all browser games would be brilliant and totally different from one another, no. They're divided into genres of their own.
The mafia rpgs.
The text based strategy games.
The village builders.
The text based sports management games.
The action point games.
Heroes of War and Money is different, its a turn based pvp game, you pick your faction, join someone in a 1v1 battle or a group in a 2v2 or 3v3 battle, then the game switches over to battlefield done in flash 8. Its great if you like turn based stuff.
http://www.heroeswm.com
Pardus is also unique, its a graphical space rpg. Players can actually build buildings from low levels which other players will see on the map. There are different factions, and the usual point a to point b and kill something quests. Its mainly the level of interaction with the game enviroment that attracts people to this.
http://www.pardus.at/
Absolute Terror is a graphical turn based pvp game, it functions like the urban dead but with better graphics. Its based on the cartoon Neon Genesis Evangelion, you pick a faction, Nerv, Angels or Seele. Nerv have to protect their headquarters, Seele and the Angels have to break in. You start off with just 1 unit and everytime you lvl your squad, you're given an extra unit. I've got 7 units. Its really a mmotbs.
http://www.absoluteterror.net/
Renaissance Kingdoms is simply roleplaying the medieval lifestyle, players have occuptions and can take government positions. I got irritated with this after my animals all died.
http://www.renaissancekingdoms.com/
Visual Utopia is like those text based strategy games, but it has a visual map, which makes the game more tricky. Like an mmo of civilization. Only join when a new round starts because regular players show no mercy.
http://visual-utopia.com/
Instant Action has a few games you can play in 3d.
http://www.instantaction.com/