This applies to both men and women. If you don't keep your nails clean or kept, what else don't you keep clean and kept.
For over 20 years, I had acrylic nails. I was getting them done since I was 16 years old. Back in the day, I kept them long, red, designs, etc. Remember the 80s? I am still trying to forget

When I was in my mid 30s, I decided I wanted to start living healthy and took a healthy approach to everything I removed the fake nails. It literally took about a year for the nails to grow in and be strong and healthy. I get them manicured regularly (together with my pedicures). French/natural look has always looked best on me.
Six months ago, for a special personal event, I did have a gel set put on. I kept them through the holidays, but wanted natural again. So, off they came. It has been about three months and I they are still not healthy. It is amazing how the fake nails really destroy your own nails. They do look sexy as hell though...I enjoy scratching my lover's back or running my nails through his hair. Most people enjoy this and I really enjoy giving pleasure.
I am constantly getting nail requests from gentlemen. I love it when they are so detailed and I can help with their desires. One favorite friend loves red toe nails. I get a pedicure right before our date. I have another friend who loves French pedicures. Guys, I am sure the ladies would agree, feel free to tell us what you like if you have a particular request. Everyone's tastes are different.
As far as the guy's nails...well, keep them short and clean. I love a man's hands when he get manicures (and pedicures). That is a bonus.