Episode V: The Empire Strikes Back
George Lucas stated that Yoda was inspired by the fantasy idea of an insignificant person or creature that is found on the side of the road really being a great wizard. That's exactly what Luke discovers when his X-Wing crashes onto Dagobah, and his makeshift camp is raided by a small, goofy alien. Shortly after we realize that this diminutive, possibly insane creature is none other than the great Jedi Master Yoda himself.
His fight with Count Dooku in Attack of the Clones was also a ton of fun to watch, as it was the first time we really got to see Yoda in action, utilizing his Ataru fighting style to keep his opponent off guard. Of course, he grabs his cane and hobbles off after the fight is over, which was pretty funny.
Yoda, along with Darth Vader, stands to this day as one of the most iconic figures in the Star Wars saga, and although Yoda left us in Return of the Jedi, I imagine his presence will be felt through Luke in the new trilogy.
"These aren't the droids your looking for"
Obi-Wan is one of the greatest Jedi of all time. He is very smart about how he handles situations, and truly cares about those around him. We see him sacrifice himself, so that Luke can become the Jedi he needs to be in order to defeat the empire.
Obi-Wan could never bring himself to strike down Anakin, and for that I respect him. Anakin was his brother, and he can't bring himself to kill him.
From the first Star Wars to the last obi-wan shows he's a powerful Jedi, that will always help out people that truly need it, and is a very good example of what the Jedi order stands for.