I've been playing an old RPG* called Titan Quest. Two word summary: Diablo Clone. Diablo 2 was lots of fun, and so is Titan Quest.
One thing that struck me about the game design is that it keeps the game simple at the very beginning. You start out as a generic character, wearing generic clothing. The only thing you have to decide at the beginning is your name and gender. Very simple. So simple in fact I thought I was missing something when I created my character. World of Warcraft, which also delays a lot of complexity (talents, spells, mounts, etc.) makes you choose race, class, and appearance at the beginning of the game. Titan Quest is … spartan (pun intended).
As with many games, as you fight, you gain equipment. Not unusual. But what is unusual is that all the equipment drops are what the monster was wearing at the time! The caveat is that equipment is often damaged during the fight, and what drops can be of lower quality than what it was wearing originally (or it could be so badly damaged it's not useful). I'm not sure if the damage level depends on the battle. I'm also not sure if this game mechanic adds much. The equipment also can be enhanced with “runes” (like Diablo 2), except the mechanics are different, and IMO more fun. You have two weapon sets, which allows you to play both ranged and melee, or have an alternate weapon for monsters that can resist your primary.
What's I really liked was the class/talent system. At every level, you gain skill points, which can be used either for advancing general knowledge of an area (a class), or for unlocking a new skill, or for improving a skill. Many skills can only be learned if you have a lot of knowledge in that area. My initial instinct was to get a few skills and improve them a lot, so they'd be supremely powerful skills. However, the strategy guides I've read online suggest that you're better off learning the general knowledge first, and then learning the higher level skills. So this gave me an interesting tradeoff: if I learn the general knowledge (which also gives me better stats), it's delaying my gaining skills. I might have a harder time now, but the payoff is that I'll get the more powerful skills sooner. (Side note: with the expansion pack you can pay to unlearn skills.) I've decided on a middle path: I picked a small number of skills to focus on, and spend the rest getting general knowledge. As with many RPGs, as you add skills, you get more options of play style, not only statically (in the choice of skills) but dynamically (in choosing how to use combinations).
In addition to the general knowledge vs. skill choice, Titan Quest also delays the introduction of classes by tying it to the skill system. You don't choose a class until level 2, when you have skill points, because you have to use those skill points to choose an area of study. At level 8, after you've been playing the game for a while, you get to choose a second area of study. So now we have over 30 class+class combinations, but you don't have to pick until you've gotten a feel for the game.
I've been quite happy not having to make so many choices at the very beginning of the game. When I first start playing, I don't have enough information to make that choice. That means I'm often going to make a bad choice. Delaying a choice not only reduces complexity as I'm learning the game, but it allows me to make better choices. I think Guild Wars and Dungeon Siege II do something similar with their class system. Titan Quest and World of Warcraft also allow you to unlearn skills, which means you can explore more styles of play without starting over from scratch. When penalties for making a wrong choice are reduced or eliminated, people take more risks. They explore more. They try more things, and have more fun.
Aside from the interesting class system, I think the game is mostly like Diablo 2, down to potions and portals and “acts” and economy. This is a good thing. The graphics are incredible, looking like hand-drawn 2D art, except it's actually 3D. I've been having lots of fun. Unfortunately, I don't think I'll play through a second time. Unlike Diablo, the maps are hand-drawn and not random. This makes it more enjoyable the first time and less enjoyable on subsequent plays. Also, it requires the CD in the drive, and having to swap CDs with whatever game I get next is a huge barrier. Still, I'm going to get ~50 hours of gameplay for $20, and I think that's a pretty good deal.
*Update: [2008-07-31] Some people pointed out that there's not much “role playing” in this “role playing game”, and delaying choices may be less appropriate if it's a true role playing game.
Game worlds are typically quite static, with some games allowing you to change the world, and even fewer allowing changes that affect movement in significant ways. One of the ideas I wanted to explore was to have the world change significantly, but the coordinate system keep the player in a “reasonable” place even while the world was changing under him. The game idea is that you are playing the role of a tiny ship inside a giant creature. As you traverse the blood vessels and shoot the white blood cells of the immune system, the creature becomes more agitated. As its heart beats faster, ripples run down the arteries, and the entire creature may start moving about. The game becomes more difficult not because the enemies are tougher, but because the world itself is changing and becoming somewhat disorienting.
Turn on animation to see some movement of the map.
The article about the demo goes into more detail about the code.