Gabriele,
To receive more visibility and a quicker response, please move this post to Products, as Marketing Central is meant for marketing-general topics, not Marketo specific.
As for your question, yes, what you can do is create a smart list with the filter of "opened email" or "clicked link in email" and choose the constraint "minimum number of times". You can start with a high number (ex. 10) and then adjust the constraint accordingly to capture those who have opened or clicked the most.
Make a note that not all opens and clicks are committed by the actual recipient of the email, and that the recipient's server may have opened or clicked the email prior in order to combat spam and virus protection.