FS04 is worth the money, much better than fsx
I all depends on how much of a system you are willing to use. When FS9/FS2004 came out there were lots of people screaming about problems with the software and graphics. Took a while, but most of the problems were worked out. Same thing is happening with FSX.
I run BOTH versions. FS2004 is great, but the graphics in FSX are better! I spend most of my online flying time in FS2004 as I have many more airframes to choose from. But the visuals in FSX beat FS2004 hands down. Simple as that, the eye-candy wins.
If someone is new to the MSFS world, they couldnt go wrong by starting in FS2004. Theres just too many aircraft/add-ons to pass up. I have most of the airframes from AH in FS2004(Not to forget many of the airframes that people want to see in AH). You cant get that far right now in FSX.
Give FSX time and it will totally replace FS2004, but it will be a while.