Ehh, when I were a lad...
Yep, there were always 'better' architectures / systems / whatever around than the IBM PC. What they *didn't* have was the sheer scale and presence of IBM. A bit like the VHS/Betamax thing (wikipedia if you're not old enough to remember!), the 'best' doesn't always win. Here's my take:
As a home PC, IBM's offering was 1) bleeding expensive 2) very conservative. But then, you're talking about a very new market; home users were still largely geeky hobbyists and not major spenders. Where this beast was selling was in to business, where it was mainly about running things like Visicalc, Wordstar, Dbase II et al. The first 'killer app' that we saw was Lotus 1--2-3; that was when the conversation shifted from 'what can I do with this PC thing' to 'I want to run Lotus, I'll buy a PC, what else can it do?'
That only gets you so far. Where IBM's scale really told was in the corporate market. PCs started getting bought in for the bean counters to play spreadsheets on, secretaries (remember them :) ) to run Wordstar / WordPerfect / IBM Displaywrite (and that was important to IBM shops, believe me). Then folks started thinking 'why do we have this PC *and* a 3278 terminal on the desk?'. Lo, the birth of the comms card and the terminal emulator. IBM's 3278 emulator wasn't that functional, but because of the open architecture 3rd parties fixed that. The (3rd party) IRMA 3278 emulator sold like hot cakes in to our corporate accounts, you could do things like data transfers instead of just screen scraping and even local printing (!).
So now what you're looking at is a large market that lots of players want to get in to. And that software houses want to develop for. And that hardware OEMs want to supply to (multi-function cards, disks, graphics cards, networks and so forth). And that IBM have decreasing control over as their competitors in the PC-compatible market establish good brand reputation (notably Compaq, for instance). Ladies and gentlemen, we have a commodity. And since commodities generally only get cheaper in real or relative terms, the market expands to the folks who think 'hey, I could have one of these at home'.
At first, the excuse is that we can do some work at home. After all, one of the most common reasons given to my salesfolk in the early days of home computers was 'I can do my home accounts on it, see'. And the games were a sort of bonus. Hmm, yeah... Amazing how many copies of Flight Simulator we sold for 'work at home' PCs. Things like MS-Windows (for better or worse, add your attitude here) make it all look easier and prettier. The graphics get better, the machines get faster, the games get better and the prices fall. The smaller competitors drop out or start building PCs, leaving eventually an x86/MS dominated market.
So, after all that, what are we celebrating? Not the sheer brilliance of a manufacturer blessed with miraculous oracular powers, but rather the appearance of a machine which as much by accident as design laid the foundation for what we have today. Could it have been better? Quite probably. But 30 years later, we still call 'em PCs, even though IBM don't make 'em any more.