It began with the making of a very thorough Fallout 2 guide, and though I hadn't intended it from the start, I realized towards the end that I would be doing the same thing with Fallout. Introduction 'I must digest this information.' One aspect in which FO1 is not smaller than FO2 is in it's overall level of kickass-ness. Still, the gameplay and story are just as strong, and except for a few control (interface) issues that were improved for FO2, you are going to love FO1 just as much. Having cut your teeth on FO2, you may sometimes feel a little restricted in FO1.
Less equipment choices, less quests, a smaller world map, less perks, less NPC control (but also less bugs). Of course, it should come as no surprise that the first game in the series would be smaller than the sequel. The main thing you will find in FO1 is there is less of everything.