To my knowledge there is no standard stitch length. They can be the size you want for the project and what is comfortable for you Some like the smaller stitches. I like a medium about what would be a 3. on the straight stitch.
The important thing is they should be consistent in length. The 1/4" is WAY out of line in my opinion. We each have our preference. But I try to get a bit larger than what the default straight stitch would be.
Remember you control the stitch length and not the machine. A recent recommendation I heard is to set your machine on a slower speed if it has that feature and work to get a balance between the machine speed and the speed of moving your hands. Then, work to get the length you want.