Most improved last 10yrs: Speaker, amp, or pre?

Not many categorical sonic improvements these days. The best sounded really good years ago as it does today. The categorical improvements are in areas of efficiency, cost, size, convenience, aesthetics, etc. but not sound quality.

What about loudspeakers materials?

Loudspeaker inclosure that use solid aluminum, composites, sandwiched woods and granite. Drivers made from ceramic, wood pulp, carbon fiber and diamonds.

You may have to back up and ask, "has there been any improvements in the last years?" :)

One thing's for sure. The level of satifaction by hi end consumers for many of today's products (at all price points) is shortlived at best.

I would say that entire systems seem to sound better than those ten years ago. The reason for this is probably the effort and expense invested in assembling them. We are all aware of the insane prices for some components, that people are willing to shell out. I don't recall quite as many years ago.
The quality of sound is frequently preferable when using a currently made top notch system, but not always, it invariably is a matter of taste.
I keep systems from several eras. I always think of my main rig first for the best sound and it is the most modern. This is not to say that ten or more year old equipment can't compete. A well thought out and executed system with synergy can certainly be assembled from the good stuff from ten years ago.