Like many, in 2000 I came back to the hobby after a break of 15 or so years. There is so much more for the modeller these days. We moan about the output from the 'big 4', models wise, they really are seriously impressive compared to 20 years ago, being well finished, run a treat and are generally accurate. I know the Heljan Western has its failings - but hey, what a beast! I'll buy another without thinking about it!
Highly detailed RTR stock has replaced often kak handed kit construction (that's me, I've never been able to get a motorised kit chassis to run properly - just not my thing! White metal, brass or plastic loco bodies and wagons no problem - just the moving bits evade me. One day I'll get that Comet chassis for my 22xx to work properly). Recent RTR offerings looking so much better than ancient white metal kits and the popular thing at the time of mounting them Wrenn chassis with no underframe detail. I have a few of these, the Wrenn body going in the bin - think what they would have been worth now!
Scenery is generally better, with proper textures replacing lurid green sawdust and bright green rubbery lichen. There were of course the exceptions in their day with the likes of Chiltern Green and Pendlebury springing to mind. I think Barry Norman's 1986 vintage book (plus another that fails my memory) and new scenic materials have changed this. I remember when Woodland Scenics launched their range in the early eighties, people were gobsmacked, especially with the foliage material. They've sadly dropped behind with the likes of Nock and Silfor eclipsing them with ground textures (personally I've never seen ragged green bath sponges in real like pretending to be grass. So, come on guys, do your own fibrous grass at half the price of the Germans and you'll scoop the market).
For buildings and infrastructure, we have all these wonderful plastics to replicate stone, brick, tiles etc. In the 'old days' many would have used the printed papers that used to fade green with time. The more dedicated would (and still do) stick in individual bricks, slates, tiles and carv their own stones.
Trackwork looks better, back in the eighties we had Peco 100. SMP had just appeared on the market with their scale bullhead flexitrack, though for points, blobs of solder were the norm for chairs. I remember some of the finer layouts used the correct bullhead rail on rivetted track, though with no chairs it often looked like a contractor's light railway. Now, of course we have Exactoscale & C&L hopefully making good looking point construction a doddle (well I hope so, I have two C&L's to make).
However, one thing that cannot be bought, is vision, design, concept and creating that most difficult thing - atmosphere!