I had a lot of problem trying to actually LIKE Fallout 3. I tried really, REALLY hard, but everywhere I looked, the game looked more like a giant mess than anything else.
The devs really had a lot of trouble organizing all the systems and items and everything so that the whole wasteland could be that big and that full of freedom. But, in the end, the game ended up more like a "Wasteland Simulator". Yes, I know the game has a lot of fans. I was probably looking forward for the game for the wrong reasons.
I thought it would provide some thrilling and compelling storytelling, memorable gameplay moments and all. The game DID have its memorable moments (for example, Tranquility Lane and the march with the Bortherhood of Steel and the giant robot in the end). But, for the most part, It felt like an "offline MMORPG" experience, only without other players to interact with. You have customization, you have exploration, you have item management, you have repetitive battles and you have very generic dialogues and quests.
I don't like MMORPGs, and the reason I like RPGs at all is because they generally have above average storytelling when compared to other genres. But I know a couple of FPS games that, at least for me, brought much more immersion and memorable moments than Fallout 3, even with the fact that I didn't have the option to choose dialogue or customize my character.
And, on top of that, the game animations were very bad, the visuals weren't nearly impressive, all dungeons looked pretty much the same, the same voice actors are used for thousands of characters and they sound totally the same, there were A LOT of bugs etc.
I admit I played the first two Fallout games very little, but I've heard they're better when it comes to storytelling and they're more consistent than F3 when it comes to general engine and systems (of course, the games are very simple and 2D, no reason to have that much bugs). I wished Fallout 3 was smaller, but more polished.
Anyway, I was getting excited for New Vegas, because of Obsidian. I'd give a new shot at Fallout, but the trailer kinda got me disapointed. They can redeem themselves by making the storytelling good, but the engine problems will most likely still be there. I'll forget about the lack of polishment if the story is really, really, REALLY great, but if it's not, I won't give the Fallout franchise another chance.