Actually I encountered this very same situation when I was trying to get Millertime/Tania (my gf) to play ST. Mostly it stemmed from me not having much local competition for ST without having to drive 20-30 minutes to get to an arcade.
First off, you can’t start off by boasting that new games suck and old games are better. You’re not going to make any friends doing that, and it’s a terrible sales tactic. It helps to just let them try the game at a casual level first. Just ask them if they want to try a new game, preferably at your house or arcade or whatever. If they’re stingey about paying $0.25 to play, you can let them borrow a a quarter. Suggest a newb-friendly character to play. Someone that’s easy to pick up and start having fun right off the bat. An obvious favorite of mine is Ryu, since he has just about all the tools he needs to win a match, but generally has a pretty simple play style.
I try to ease players into by teaching them the basics. Let them get a feel for the game on their own, but offer to give advice, suggestions, helpful hints, cheap and abusable tactics, to get a jump-start on their win/loss ratio. Once they pick up on that, it helps to reinforce the fundamentals of the game you’re trying to teach, as that skill will carry over throughout a variety of fighting games. After playing the game for a bit, even Millertime learned that ST is a game that focuses purely on fundamentals, and she’s actually transferred that skill over to SF4. She realized that she can fuck up most scrubs by applying basic strategy and execution in her matches that’s core in ST, but most new SF4 players don’t know about. This only helps strengthen her resolve to improve at ST, because she saw that it directly affects how she plays Honda in SF4, to destroy people who don’t understand how to properly block, zone, and feel momentum shifts.
Like for me, I taught Millertime how to store the ochio and do tick throws, since they’re very powerful in ST, as a cheap and easy way to win certain matches. She loves it. I also taught her how to properly do hands and use j.mk as the primary jump attack. Hands does fantastic chip damage, is a great way to counter poke, and it builds meter. J.mk is his primary jump attack because it has awesome priority, usually trades in his favor or equal health loss, and leads to a variety of tick throw and frame trap setups.
It’s to the point where she greatly enjoys fighting disadvantaged matchups, because she has to work so hard, play extremely technical, and have near perfect execution to win her toughest matchups. It really forces her to adopt a more strategic, patient, and analytical style of play, that helped give her a bit more range on how she approaches a variety of characters, playstyles, and game engines, across a multitide of games.
tl;dr. Being a good teacher and being supportive of your players, can help convince others to play older games, as long as there’s a strong scene around you.