The comparison between "Friends" and "How I Met Your Mother" has been talked about plenty of times during the run of the latter show. On the surface, they look pretty similar as they're about the work, social, and love lives of a group of friends residing in New York City. The comparison between these two shows, in particular, occurs the most commonly, over other NYC-based sitcoms, most likely due to the proximity of air dates between the two shows. "Friends" had a ten-year run, ending in 2004. Only one year later, "How I Met Your Mother" started with what ended up being a nine-year run.
The appeal of the show "Friends" is two-fold. There are either people who love it for the nostalgic value - the people who grew up with it, or people who love it in the way that makes it almost have a cult following. These are the types of people who constantly make "Friends" references, or talk about who the Chandler of their social group is. From what I've experienced, "Friends", compared to other TV shows, is that one the most casually referred to. So much so, that people I know who haven't seen it, still briefly understand the implications of what it means to be a "Monica." Or worse...a Ross.
Speaking of Ross - the whole topic of his personality and behavior powers a debate between fans, and even non-fans, but more importantly, has caused younger viewers to not give the show a chance. This is because some of the issues he gets himself into, or even the lines of dialogue that come from his mouth would now be considered social taboo if said or done by one of your friends. For example, while the show intended Ross to be the most romantic and least misogynistic of the three men, the viewers of today view him as the opposite and have sparked discourse criticizing his “nice guy” persona. In addition to his character, the general humor of "Friends" is now commonly considered "dated" as it has been deemed by some as body-shaming, misogynistic, homophobic, or otherwise problematic. As a result, younger viewers are not grabbing to "Friends" the same way. Older fans, in my experience, don't defend this kind of humor, but still, don't let it pollute their memories (or re-binging) of the show.
It seems that the appeal of "How I Met Your Mother" is partially its character-centric storylines. "How I Met Your Mother", unlike "Friends", has a narrator. This means that the show can play around with flashbacks and flashforwards, which brings in a new type of humor rooted in situational or dramatic irony. Additionally, topics such as frustration of a lack of relationship, loneliness, and friendship are seen through a first-person lens, which may make it more relatable to some.
In terms of humor itself, I personally have not seen a lot of criticism (in comparison to "Friends"), even though the humor is just as blatantly, if not more, sexual. I haven't seen much discourse about how problematic the character of Barney Stinson is, the way I've seen a plethora of Ross-shaming articles.
Despite their incredibly similar storylines and characters, fans of each advocate that their preferred show is superior, not by naming reasons, but by talking the other show down. So is the appeal generational? The age of sitcoms that "Friends" was present for taught 90s adolescents and adults to prepare for Y2K and onward. While the backstory for each character on the show may not be the most relatable, their personalities remind you of your own friends - which is what the appeal of the show is.
Meanwhile, fans of "How I Met Your Mother" commonly talk about their takeaways about what the shows have taught them about coping with romance, loss, breakups, and relationships as a whole. This is something that millennials may prefer as dating nowadays can be described as "turbulent." By having an established couple from the pilot to the finale, as well as a range from single-and-loving-it to single-and-hating-it characters, viewers can identify with the opinions of the characters, over the characters themselves. Thus, the relatability isn't bound as two-dimensionally, and viewers can empathize with different characters at different points of the show.
There's a place in my heart for both shows, and I've never been one to compare them, as I watched them at two different parts of my life in completely different ways - binging a season in a day vs. week-by-week from sophomore year of high school to sophomore year of college. I have visited both the set of Central Perk in LA, as well as been to the bar "MacLaren's" is based upon in NYC. I think that both shows are equally as enjoyable and while I can see why certain age groups would prefer one to another, I will continue to keep rewatching both.