heres my thoughts
10. The mouse - This revolutionized hardware interface on a pcbefore this there was jsut keyboards!
9. 1ghz + speeds - this is where pc hardware really started doing more than what teha verage user needed , (althought modern OS'es would totlaly gimp the first ghz cpu today , technically you can grab win 98 and still browse the web if that is all you want a pc for , which happens to be what most users want one for). also should be noted because hitting the 1 ghz ,milestone was the first thime intel lost a tech race, the first 1 ghz cpu was an AMD slot A athlon cpu, which was replaced with a socket version of the 1ghz athlon, even before intel got thier first 1 ghz out .
windows - windows 3.1 gave the few folks that used it a glimps of waht the future could hold for pcs
windows 95 - This was teh realization of what win3.1 had tried to do, after win 95 PC's became a viable product for the mass market
the internet- it came a bit before windows 95 , but in all honesty this was the driving factor that made pc's common house hold items.
Two button mouse- the idea of a mosue with two butons was revolutionary , sure it sound's small, but can you really iamgine navigting an OS with just one mouse button ?
mouse wheel - not long after windows 3.1 came out it was realized there needed to be a quick and easy way to scroll a window page. welcome mouse wheel , again not a major revolution , but the mouse wheel is used in nearly ever modern application in exsistance today. Today if fuctions as a scroll bar for window opages , web browser pages , as well as a way to zoom in and out , in a large variety of 3d applications as wella s 2d paint applications.
3ds Max/maya - normally i'd toss this one out of the lsit cos i'm thinking of things that directlya ffected pc's , (it's why i disagree with wireless being on your list , that revolutionized communication not PC's). however , consider this , recently a lot of so called "experts" are all sayign how pc will die blah blah blah. but programs like 3ds max and photoshop or coral painter , are the main reason why these guy's wordsa re total BS. in short the invention of 3ds max solidified the PC as tool for multiple entertainment industries (namely the movie industry and the game industry). It was created in 1989 namely for use in generating movie effects , and was later caried over to the game industry when that industry moved to 3d. for the most part the movie industry started using maya which was bassically a redisgn of 3ds max done specifically to cater more to the movie industry, but 3ds max today still stands as a reason why P{C wil NOT die , at lest not in the work force , you can't seriously run this application on a mobile device , msot lap tops can't run it half as well as a modern lower end desk top , not to forget a full blown power workstation.
DSL - sure it's not as good as fiber optics or even cable , but it was the first form of broadband , and iit is stil the only option for soem areas. thankfuly dsl speeds have increased some with time (my dsl conection is just good enough to stream 1080p movies off net flx, or play online games , not sure how it would handle onlive's streamed games though 😛 ). point being this really opened up what was possible with the internet ...high quality porn anyone ? (joke).
and no these are not in order of importance , because hoenstly i think they all had huge importance . with otu any oen of these milestones , the pc would not be what it is today , and maybe then those a--es that think it wil die might atually be spekaing truthfully.