Diablo-esque, but all online & free with more customization & area's
That being said, Guildwars allows you to play in the 3/4 overhead view or zoom to first person perspective.
You can play solo, or with other people. Even solo you have a number of henchman npc's to fulfill the roles in a group. Either way, the game is quite difficult compared to others. You have minor quests and main storyline quests. When you complete one of the main quests you get a cinematic movie that leads to the next area. All items you get can be broken down for use in creating new armor and weapons. You can add runes to your armor to increase your stats. The max level has only been 20 for quite some time. When you level you get skill points to train. I find that once people discover the "uber template" everyone is a carbon copy which is the case in guildwars.
The great part is that its an online only game and totally free. Well, you have to buy it, but theres no monthly fee. And you can PVE & PVP all you like.
The Factions expansion adds a number of pvp instances to go with the original battlefields. The graphics and landscapes are quite beautiful. But most of the time you'll be attacked by large groups of monsters and have little time to explore safely. Everything is instanced to your group so you'll never run into other places in the wilderness. The only places you run into other people are in main towns or cities, or in the battlegrounds.