You're still better. Believe me.
I'm not saying I'm not - I'm just saying no proof of my skill-level with guitar has been provided, and as such, you are assuming without evidence that you are not as good as I am.
You've fallen into the trap that people using "I've done this for years" as if it bolsters the quality of their opinion are hoping that people reading/listening will fall into - that you'll assume those years mean significant time and effort spent with an intention to get better, rather than just keep doing the same old thing over and over again.
Would a count of sessions-run be more useful?
Absolutely. Anything that is an actually quantifiable measure of effort spent or how people felt about that effort is inherently superior to a vague notion that perhaps effort was spent and quality was achieved.
For example if I told you I've run about 1800 sessions over the last 34 years, about 99% of which were in three ten-plus year campaigns*, that should at least inform you that I've got some experience running games (as shown by the session count), and that whatever I'm doing I'm doing it right enough that the players keep coming back for the next session (as shown by the campaign length).
Precisely, more or less. That's what I am talking about when I point out that "I've been a DM for 34 years" doesn't convey important details that are necessary in order for me to make a comparison to how much effort I've put into things relative to you.
If we just stuck with your "34 years" and my "25 years" most people would assume that you've put more time into the hobby than I have. But if we mention how many sessions we've each run during our years, your 1,800 seems like the smaller amount of time than my nearly 4,000. And if we factor in the number of hours of game-play for each of those sessions, who appears to have put in more time may flip around yet again (like if your session are usually 9+ hours long on average and mine only average out to 4+ hours [I think it's more like 6, but it's dropping over time because of life schedules limiting my group to 4 hour sessions lately, and I haven't re-done the math lately]).
But the length of your campaigns doesn't actually convey that people were coming back because of the quality of your game (unfortunately, that's a really hard thing to actually to quantify).
And the same sort of things can apply to guitar playing. You've been playing for 25 years but have you ever been in a band for any length of time? If yes, then obviously you're good enough that they kept you around...and thus are better than me.
You are assuming "I'm in a band" and "I'm in a band that people actually want to listen to" are synonymous when they are demonstrably not. Any group of people that owns instruments and tries to play them together, no matter how lacking in proficiency they all are, can accurately say "I'm in a band."
Middle-schoolers that just got their very first woodwind yesterday are in a band, and are unlikely to get kicked out for the quality of their playing (at least, in places that haven't completely gutted the music department due to lack of school funding), and professionals with stunning skills get tossed from bands pretty frequently for reasons other than their quality of playing. So me saying "I was in a band" doesn't necessarily rule out me, and my band mates, all being absolutely awful at playing our instruments.
Much like someone saying "I've been DMing for this group of players for about a decade now" doesn't rule out that they are awful at DMing and the players keep letting them DM because none of them want to do it and they don't have any other options that keep showing up and saying "Hey guys, wanna play some D&D?" - which to add a brief anecdote, is the situation I found a group in when I moved to my current city; I found a group, joined them, started DMing for them, and they never wanted to have their old DM run the game anymore afterward.
