Part of what made both Joey and Chandler so funny were their hilarious facial expressions.
Joey's 'shocked' expressions were gold.
For sure. The one where Ross dates Janice ends up her telling Joey, "Well, Joey, that's two...," before laughing and leaving, leading to Joey giving Ross that big-eyed HOLY SHIT look.
Switch Rachel and Monica, and that would be my list
Monica and Rachel kind of switched places over time.
Early on, Monica was funny, while Rachel was usually a total bitch (albeit a hot as hell one). Just look at how rude she always was to Julie, who had nothing to her ever except date a guy Rachel was secretly in love with.
Later on, Rachel was funny, while Monica became really irritating and completely self-centered.
I thought S5 was the worst. At least any Emily episode.
Emily didn't bother me, and she was in much more of S4 than S5. She was talked about a lot in 5, due to the marriage being in limbo and then the breakup, but we saw her mostly in 4.
And Season 4 is, for me, hands down the best season of the show by a wide margin. Everything came together that season.
I don't really remember much of the earlier seasons. I've seen it all at least twice, with some of the latter seasons more times, but to me those were more enjoyable. I don't know which season it happened, but Monica and Chandler hooking up was like a turning point, and most of what I remember liking (memorable episodes and such) happened after that.
I think the turning point was Chandler and Monica getting engaged at the end of S6. The show was very hit or miss after that, after being mostly hit prior. Season 7 sure wasn't helped by the character Tag, who was not only an awful character, but was played by a terrible actor.
Plus, the serious moments early on were always done well, while later on, it's like they were too worried about the comedy always being at the forefront.