Whilst you can start by doing this exercise based on your own experience of buying and playing games you could get a better idea of what might sell by including data from other people you know.

A Suitable table might look something like this …….

The headings can be extended to include other aspects of games such as 'Easy Rules',
Colourful container, etc, etc.  Create a list of additional features that should be included in a travel game and then select from that list the ones you intend to include in your table.

Once completed you could colour code your answers with, say red for a bad feature, green for a good feature and yellow or orange for something that isn't too important. 
Your final table should now be really easy to understand and anyone knowing the 'key' you have used would be able to tell your favourite games almost instantly.      You can use the
colour coding to decide what features are found in your best games and these features could become a part of your specification.
Remember,  you are trying to design a new travel game - so  a peg-board version of
Monopoly may not be suitable as there are many other items that are a part of that game - such as the money and the 'chance cards' that would need re-thinking.   So … something new and innovative is needed.  Don't dismiss any new ideas - anything could work !

Whilst you are designing your game you could give some thought to the counters that
are used.  A game can be dramatically improved through having exciting playing pieces.

Researching geometric shapes,  or extending the them of the game - as in board games that have a detective theme and include all the items that are  associated with crime or detective work - may be good research directions .