First of all you shouldn't do it. If a user have installed other plugins, it is because he/she want ot use it, even if your plugin provide all functionalities of that plugins, who say that for the users your plugin is better than others?
And if that users already have tons of settings with other plugins and see them disappear installing your plugin? I bet that users immediately unistall your plugin (and if there is possibility very low votes will come in that case).
Also consider that another plugin can use the same technique to remove your metaboxes. An the another plugin will remove the metaboxes of that plugin, and so on...
What it will be, the war of metaboxes?
My suggestion is to add your metaboxes and let users decide what metaboxes to leave and what to remove (unistalling plugin or unchecking the metabox from the "screen help" tab).
Finally, note that you can't remove metaboxes of a plugin if you don't know the id of those metaboxes. So to do what you want you should install all your "competitors" plugins, look at the id of their metaboxes and remove them using
And if a plugin get updated and change the id of its metaboxes?
Believe me, it's and hard, dirty, no-benefit work.