Much of EU at the time before The Prequels, which kept our fandom thriving till those films dawned, depicted the Jedi more in line with The Original Trilogy. Rather than monks, Knights and Samurai with mystic powers. The concept of Jedi Knight was a focal point, especially in the games named Jedi Knight with Kyle Katarn who was not a conventional Jedi, he even tapped into the dark side and had Pontentium view of the Force, that there is no light or dark side until you choose to use the powers for good or bad, that the dark side is not the corrupter, it is corrupted using the Force, an intriguing view to say the least, though not at all Luke Skywalker’s philsophy, especially after The Throne Room with the Emperor and later Dark Empire when he falls.
What was nice is the Jedi had divergent philsophies or sects, but they were One. There were core principles or dogmas, but denominations were allowed, including The Altisian Jedi who married and trained more than one apprentice. This made the Expanded Universe strong in my humble opinion, you could find a Jedi sect that fit your personality more, and then the dark times came… The Prequels. Now I love the Prequels, but what they did to the Jedi and the Sith was tragic. To the Jedi they made them more akin to Franciscan and Buddhist Monks who happen to have laser swords, and caught up in bueracacy of the Republic. When Ben told Luke about Jedi Knights, the sense you got was they were warriors that served the Republic in times of need, not intrinsically connected and playing politics as much as the Senators. Then with the Sith not having been around in ages, and the Rule of Two, GL limited in that time period how many Sith antagonists there could be and when Sith could appear. In the OT and EU none of these restrictions existed for the Jedi and Sith, and its a shame that Disney is not stuck because of these GL ‘gifts’, unable to really make great new Sith Lords anywhere before The Prequels, during them, and at least up to ROTJ.
Another thing is the Kenobi tells Luke in ROTJ, “Your feelings serve you well, they do you credit, but they could be used to serve the Emperor.” That line is so crucial, the “There is No Emotion,” clause of the later Jedi Code was not present, the issue was controlling your feelings, that they can serve you or they can be manipulated by someone like The Dark Lord of the Sith. I hate GL changed that to emotion is bad, and you should purge all attachments. It was attachment that Luke used to save his Father.