Any number and combinations of shrubs, perennials, & small trees (large shrubs) would do wonders to hide everything in the neighbor's yard. Start looking around and see what plants appeal to you.

Fence looks to be about 5 ft tall max, judging by the chair in the picture. Pretty much any shrub that works in zone 3 and gets to 5 ft should work. Group shrubs, don't alternate anything, though you could repeat a favorite maybe 3 times. Look for a little evergreen, but also spring bloom, fall berries and leaf color. Plan for perennials in front of the shrub border.

The tree on the right seems to be doing well. I would plant another like it.

I'd have a mix of flowering shrubs and trees. Like dogwoods, mountain laurel, hydrangeas. That way you can keep the flowering season going.

If you want fruit, you can espalier an apple or pear. High bush blueberries are an option, but it might take a while before they top the fence.

Seems like everyone has great ideas!