If you were previously using a zoom, you might want to go back through exif data for photos you've shot and liked the look of.
Easy to do in Lightroom or other photo database programs.
I'd say, at least for me, 35 on a full frame camera. For what it's worth, I used to use a 28mm on a 'crop frame' camera exclusively. That's about a 40 on a full frame, 5mm wider would have been great. (That lens needs a repair, so I'm using a zoom)