I was hesitant about Fallout 3 mainly because of Oblivion, but it and I will have to get married if I keep playing it this much. I've been playing it for weeks. I played through it, modded it, and I'm on my 5th playthrough. It's not quite as hardcore as previous fallouts in ways that no modern game can seem to get away with, but it's fun, it's an RPG with a nice implementation of player skill vs character skill (even with guns), and unlike every single Bethesda release I can remember, this one isn't a simplification of their previous entry. They learned from Oblivion in many ways and corrected some particularly egregious errors, and that was a game I only started to enjoy with dozens and dozens of mods active. I could go on for pages, but I enjoy this game aesthetically, it's (now) got a great pace, it's (now) a great challenge, and I genuinely find the feel of it - the control, the voice acting, the explosions, the character development, the weapons - gratifying to play and rewarding of a diversity of play styles. I can't really see an RPG gamer skipping this one in good conscience. It's a whole new situation from the previous two (which I also love), but it's still Fallout to me. And by the way, with mods, the sex, drugs, and rock and roll are all here in their shameless glory.
In any case, we're now talking about a game with 30+ mods released for it daily. There's something to be said for a living, breathing entity that can be shaped in many ways into the game you want to play. I'm currently playing with XFO, a mod that makes the game much, much harder and better balanced. It's got severe radiation from water and food (and the option to
need water and food), fewer skillpoints per level to force you to develop your character intelligently, higher explosives and big-guns damage, new perks, and a whole lot of other things, all of which you can choose which parts to add. I'm also using Martigan's Mutant Mod, which lets all sentient characters loot and carry around stuff from their wasteland adventures, adds the number of spawned enemies (or allies), and changes the variety in every given encounter. It does this by making enemies slightly different sizes with different textures and, most importantly, different stats and AI behaviors. The raider with a missile launcher may or may not know what he's doing with it

Oh, and ghouls? If you remember a hallway or two with 5-6 ghouls, imagine the same hallway with, I kid you not, 30-50 ghouls. It's like a wasteland zombie invasion. Bring a shot-gun or a mini-nuke. Another mod I feel like I should mention is one that lets you construct your own robot guards and travel the wasteland with them. Finally, a mad-scientist simulator...lol. I'm also considering incorporating part of a mod called FOOK, which adds dozens and dozens of weaponry and armor from the community and puts them into the same leveled lists, as well as a 'roleplayer's alternate start' mod that lets you start as members of other groups than the Vault, such as the raiders, the slavers, the wastelanders, the brotherhood of steel, etc, with severe consequences on how you play the game.