Traditionally, one of the most popular project management software is MS Project, but it would be really hard to form up the comprehensive rating to finalize the competition among popular project management tools, because there are too much of different properties to compare in order to find out the unambiguously best one. Actually, it is possible to identify the most popular project management software only in context of certain needs, because every product has one or several robust aspects which are much better than competitors have, while other sides can be really weaker. 

This is quite OK as far as developers cannot create product which is absolutely perfect in every respect. You may find a lot of web-sites where the tops of popular project management tools are represented, and you may be surprised that these ratings are completely different from site to site, having even completely different list of products reviewed. This is normal as well, because probably just different requirements were taken as a basis for comparison.  

The main aspects creating general project management popularity for software are first of all sufficient functionality covering needs of the widest audience and a moderate price which makes software accessible for a big number of users. But actually there are a lot of other factors, for example ability of software to support the most popular project management methodologies such as Scrum, RUP etc, or possibility to support collaboration of multiple users. Let us represent one of the most popular project management software which was recognized by TopTenReviews as one of the top rated tools (2^nd place):

VIP Task Manager is one of the most popular project management tools in terms of tasks scheduling, assignment, real-time controlling and multi-user collaboration. This teamwork client-server software features three agile modes Task List, Task Tree and Calendar where you can freely operate with team and individual tasks to define them with multiple attributes (standard and custom). In spite of the fact that it cannot cover all the wealth of specific project management functionality, this product is a great solution for those who need easiness in use and configuration, and its moderate price makes it attractive for small/medium business companies.