Fallout 2 is roughly three times as long as the original game. Rather than having an expanded main quest, all this extra space is used for vastly expanded side content, including dozens of side quests and many entirely optional cities. Thanks to excellent quest design and writing, this side content gives you ample space to develop your player character and define your own playstyle. You have an incredible amount of flexibility in how you solve quests and approach challenges, 95% of the game can be completed as a pacifist, for example. Unfortuantely, most mechanics remain unchanged fom Fallout 1, and said mechanics weren't really built to support such a long game. Character progression can slow to a bit of a halt, and the companions are still a pain to make use of. Though I really like the main quest, its unfortuantely linear compared to how flexible the side content is.
Invisible War is worse than the original game in almost every way, and Deus Ex was far from perfect. The inventory is bizzare, the combat is repetitive, the story is confusing. However, Invisible War contains several open hub areas, full of side quests and exploration. I really enjoyed these sections, and they're unlike anything in the original game. Invisible War isn't a very long game, and I felt that it was worth playing for these sections alone, even if the more linear shooting sections are garbage.
Fallout is a complex, and dense game, but also short and tight. Every location is part of your essential journey, and almost evey quest ties into the main story. Every choice, from character creation up to the ending, feels impactful, both to your mechanical progression and to your impact on the world. Fallout's art, world design, and world building are all excelent. The wasteland is atmospheric, despite the pixelated graphics and brown colors. Unfortunately, many mechanics and solutions are obtuse. Skimming the sixty page manual is basically required to get started, and even then, you'll be tempted to use the wiki frequently. This is worst in the end game, the last few quests and dungeons are full of confusing things. Fallout will demand patience beyond many people.
Exploring the Capital Wasteland is a blast, and enough to make Fallout 3 worth playing. The enviroment is immersive, detailed, and large, there's so much to discover and experience. Sudo-survival mechanics keep looting relevent, and especially in the opening hours, searching for valuable items can be tense and exciting. Unfortuantely, the RPG and FPS game mechanics are particularly weak. Aiming feels unreliable, the guns feel unimpactful, and the VATS "bullet time" system forces you to weight through endless slow motion animations. Character building options are trivial, there are few quests and even fewer complex ones, and most choices are unimpactful. Fallout 3's basic game mechanics can not support its long length or huge world. The main quest is really, really bad, and most of the DLC quests are even worse. I like the Pitt DLC, and some of the base game side quests though. There's fun to be had in Fallout 3, but huge parts of its runtime are very weak.
