There is no doubt that research work is considered 'a feather in your cap.'
Especially if you can be listed as author or part of the team.
Most people seeking competitive residencies take the same approach when attempting to get into medical school-they do whatever they can to make themselves more competitive. Sometimes if someone is weak in one area, they may choose to work on their competitiveness in other areas.
Can you get into these programs without research? Most of the examples you gave were subspecialties, so performing well in the basic residency training would be a great start, also try to match at the same university that has the fellowship that you desire as well. Obviously this will make for better connections all around. Gen Surg-do well for the clinical rotations, smoke your board exams, and talk with come current surgical residents or interns and ask them what made them competitive for their programs, etc.
I would finish by saying most medical students match very well without ever having a research project prior to or during medical school.
I hope this helps.
