I think it should be possible to import prefixes (such as Madame or Monsieur) but you need to make sure that the prefixes are created in CiviCRM before you import the data (/civicrm/admin/options/individual_prefix?reset=1).
Also, the Labels in CiviCRM need to be exactly as those in the column of your import file.
Or do you want to import greetings (email or postal greetings)? I am not sure, if this is possible because they are usually generated.
You could try to use something like this for generating a greeting depending on the prefix (just enter it here: /civicrm/admin/options/email_greeting?reset=1):
{capture assign=c}{contact.communication_style}{/capture}{capture assign=p}{contact.individual_prefix}{/capture}{if $p=="Madame"}Chère{else}Cher{/if}{ }{if $c=="Familiar"}{ }{contact.first_name}{else}{$p}{ }{contact.formal_title}{contact.last_name}{/if}
CiviCRM would the create an appropriate greeting depending on the communication style (formal or familiar) and the prefix. Please note that for this approach you need to have smarty enabled.