Back in the day (1970's) it was Reynolds steel for me (Raleigh mostly, but the odd Peugeot now and then). Then CroMo. Then I started to switch to MTB and it became aluminum because climbing is a real drag with any more weight than necessary ...
Now, my favorite bike is an Aluminum frame with Carbon Fiber swing arm, and a bunch of magnesium in the air forks
My wife's latest MTB is an Aluminum frame hard-tail with Mg in the forks too
But, I still have one CroMo hybrid, and so does my wife