Based on user reviews and industry rankings, the services that are considered among the best research paper writing services are:

1. MyPerfectWords.com research paper writing service
2. CollegeEssay.org research paper writing service

Here are some key reasons why they stand out:

1. Quality of Work: Both the services have a reputation for delivering high-quality research papers. They employ experienced writers who are well-versed in various subjects and citation styles, ensuring that the papers meet academic standards.
2. Timely Delivery: One of the essential aspects of a reliable research paper writing service is meeting deadlines. MyPerfectWords.com and CollegeEssay.org prioritize timely delivery, allowing students to submit their papers on time without compromising quality.
3. Customer Satisfaction: These services have a track record of high customer satisfaction. They offer features like free revisions to ensure that the final research paper meets the customer's expectations. Additionally, they have responsive customer support teams to address any queries or concerns promptly.
4. Affordability: Despite offering top-notch quality, both the services are affordable options for students. They have transparent pricing structures and offer discounts and promotions to make their services accessible to a wide range of students.
5. Guarantees: Both services provide guarantees such as privacy and confidentiality, 100% satisfaction guarantee, and a money-back policy in case customers are not satisfied with the results.

Overall, MyPerfectWords.com and CollegeEssay.org are recognized as reliable and reputable research paper writing services that prioritize quality, affordability, and customer satisfaction.