Didn't read the entire thread to see what's been recommended or not.
For me, the metal 9mm full size pistols that I consider classics and will keep their value are the all metal Beretta 92FS (or any related 92 series), Sig P226, and CZ75b or later.
I have the P226R: aluminum frame, grips can be wider (if yours didn't come with E2 grips and appropriate mainspring) or narrower if it is new or install the E2 parts. The factory single action is nice. Really nice, nicer than a factory CZ75b, or factory SP-01. I installed a Short Reset Trigger and it makes a noticeable difference in reset if you care about that, but it's just for enjoyment, probably wouldn't affect shooting if you practice. Some go with a lighter hammer spring to decrease the DA pull weight as they are over-sprung for reliability worthy of military service. The stock 3 dot sights are pretty big / wide and I like that. **(edit to add detail on the trigger, since I realize I don't like it when someone says something is "nice" without explaining. In single action, there is a distinct wall of resistance. The trigger does barely move pulling across this wall but the release is very crisp in my particular pistol. I can't actually feel the trigger move right before it breaks, I can only see it if I watch it with my eyes. All in all it makes for a satisfyingly crisp single action break that may be stiffer than a 1911 trigger, but crisp. Double action pull is stiffer than the CZ SP-01 but shorter.)
I have a CZ SP-01 Tactical (decocker). Steel frame. The full length railed dust cover does add more weight up front. If I could do it again, I probably would go with the version with the safety. Decocker would be nice for carrying, but I have more suitable guns for carry. The Decocker verison means adding competition parts from CajunGunWorks is more complicated. Factory night sights are like standard Meprolight, a little small / narrow, but pretty standard. Trigger is nothing to write home about, a bit of creep in single action. But single action is relatively light, just not crisp. The reach to the trigger in Double Action is better when placed in half cock. (Sig P226 doesn't have half-cock) It's a rolling double action break, not a distinct wall. But I have a couple other pistols like that so I'm used to that. I got it out of nostalgia and the design, the first pistol I ever shot was a 75b which I hear swings/handles better, but has no rail. The SP-01 is a nice looking pistol, in my opinion. The full rail gives it a pitbull high tech look. Like it should shoot lasers or something.
I don't have a Beretta 92FS, only shot a few. Aluminum frame. Just beware that racking the slide may take some adjusting to avoid decocking or putting the pistol in safe, since it's right where your thumb or index finger might be. The Taurus PT92 would be a very similar version with a frame mounted safety, and one of their better made pistols. Just a bit of risk with Taurus customer service though. I can't comment about the trigger since it's been a while. The 92FS doesn't have a replaceable front sight, it's milled into the slide. You would want a 92A1 to have a dovetail in front to replace the front sight to your liking.