At least, some models were! And that's, depending on where you lived in the heydays of CD-i around 1994, pretty much agead of its time. Widescreen formats were pushed through worldwide around 1997 although I remember in The Netherlands at least we had widescreen televisions before that. But we think it's safe to say in 1994 the option to output widescreen was already a bit ahead of its time. Nowadays we cannot think of anything different but most CD-i titles were still optimized to play in a 4:3 format, original CRT televisions were all like that. In 1992, it was Philips who pioneered with widescreen CRT screens and pushed the new format, especially with movies in mind and the future of entertainment. With Polygram being part of Philips, they were very well informed about the importance of a 16:9 format. And when movies were indeed going to be interactive in the upcoming CD-i standard, 16:9 video output was also going to be a part of it. Your CD-i player was already widescreen-ready in 1994! That is, if you had the right version: For example: it doesn’t have the option on a 220/37 but it does have it on a 220/57!
Jorg Kennis about this: "Any CD-i title can be viewed on a wide screen TV set using either one of the options offered by the TV itself. No special resolutions adapted to the 16:9 aspect ratio are defined for CD-i, however a picture can be 'squeezed' within a normal 4:3 image that can be 'de-squeezed' at runtime by the TV-set. Please be aware of the fact that, in contrast to any DVD-Video player, a CD-i player has no build in facility to correct the display of a widescreen image on a normal 4:3 display by filling the screen with black bars at the top and bottom. When a widescreen title is also to be used on a 4:3 display, the content should also be stored in this aspect ratio on the disc. Some consumer CD-i players (like the Philips CDI-220/60 and up) provide for a 16:9 switch in the player shell. This switch records the setting in the CSD (See What is the CSD?), which allows for applications to look for the connected TV format. When such a player is set in 16:9 mode, the player's startup shell is displayed in wide screen, but when a CD-i is started, the screen is switched to 4:3 mode. An application that interpretes the aspect ratio setting in the CSD may then turn the screen back to 16:9. This CSD entry is an extension that is not specified by the Green Book, and there are only a few applications that supported it."
[Thanks, James Boner, Jorg Kennis]