Back in the day, you'd have to drive to the Egghead Software store to buy a game. You had perhaps ten, or twelve games from which to choose. It would come in a cardboard box, typically containing four to eight floppy disks. After feeding the disks to your PC and reading the READ.ME file, you'd spend the next day and a half cooking up a set of customized autoexec.bat and config.sys files before the game would run. You had to determine not only whether the game needed extended, or expanded memory, but also which TSR's (Terminate and Stay Resident programs) needed to be loaded and in what order. Every game that you bought required their own custom autoexec.bat and config.sys files and you had to somehow manage these files to ensure that the correct files were used to boot the PC, for the game that was to be played. Playing a different game required rebooting the PC, with different, customized configuration files. Playing a game on a PC was strictly for computer enthusiasts, mere mortals need not apply.
Windows simplified the situation significantly, but there always seemed to be 25% of my games that inexplicably refused to run. One spent hours scouring the game publisher's bulletin board (remember them?) looking for clues and patches, which had to be manually applied. Sometimes they resolved the problem and sometimes no.
Then Steam appeared on the scene. They had an awesome selection of games. They published awesome games. Does anyone remember how groundbreaking Half-Life was? They had user reviews. They saved your progress, so you wouldn't loose your progress when you reloaded Windows (frequently necessary), or when you purchased a new PC. Most importantly, all of their games ran. All of their games were automatically patched in the background. And, all of those 25% of games that would never run for me? I could activate them on Steam and THEY WORKED!!! Not only that, but you no longer had to sneak into work after hours, in order to play LAN games with friends. You could play "LAN" games over the Internet. How friggin' cool is that?
Steam wasn't merely the first game service that worked. Steam revolutionized the entire friggin' game industry!
In later years, Steam has pressed for an alternative to the near monopoly that Windows has enjoyed on PC gaming, by contributing to the Linux code base, developing a gaming-centric Linux distribution, porting their own hugely popular Valve games to Linux and selling their Linux versions for ... FREE ... to anyone who had already purchased the windows version!
Unlike the cable industry, the government didn't hand Steam a monopoly so that they could go forth and rape and pillage with impunity. Unlike some of the tactics that we've seen come out of Redmond, I'm not aware that Steam has purchased GOG, in order to put them out of business. As far as I know, Gabe never held a gun to anyone's head and demanded that we subscribe, or be prosecuted to the limits of the law. No, Steam earned their customers based on their customer's own assessment that Steam's benefits outweighed the negatives.
So, is Gabe the second coming? F%#K no! He is a businessman. He is a very successful businessman and he is successful precisely because he identified a problem and then developed a solution to that problem that exceeded most everyone's expectations. So long as his customers continue to believe that Steam's pluses outweigh the minuses, Steam will continue to be successful.