Well, as a former Amiga-enthusiast (Amiga actually means "girlfriend", so we could geek it with the best of them) I know that the originaly Amiga, the Amiga 1000, was debuted in 1983. It was released in 1984 (although I might be out by a year, 1984 and 1985 respectively!)
It had 256k of RAM and a 7 point something MHz Motorola 68000, and the first version of the Amiga's custom chipset.
Now, that computer came with Workbench 1.0. Billyboy released Windows 1.0 in 1985.
So yes, the Amiga was running Workbench before IBM-compatibles were running Windows. Now, Workbench was also superior: it was a multi-tasking operating system. Windows 1-3 (and possibly 95-98, not sure about them) were "Multiple Program Loading", but not multi-tasking. Big difference. The GUI was superior to all versions of Windows until Windows 95. Also the disk format was superior to the IBM-compatible equivalent: 880 kbytes on a DD floppy instead of 720. HD drives were available with the A4000 which would hold 1.8mbytes on a disk that a PC would only put 1.4mbytes on.
Of course, back then until about 1993, Amigas were superior to PCs for all but office number crunching. The graphics chipsets were far superior, and the games were better too.
Personally, I owned a "CDTV", which stands for "Commodore Dynamic Total Vision". The world's first CD-ROM based personal computer. A wonderful machine. Based on the A500, but with 1mbyte of RAM and in a hi-fi format (looked great). I had this networked with my brother's A1200, and we used to play network games. Great stuff.