Way back in 2001AC the legal luminary A.G.Noorani reviewed a book Muhammad in Europe: A Thousand Years of Western Myth-Making by Minou Reeves. Later on he used his experience of this book in a chapter of his very brief treatise Islam and Jihad. He has given a very handy list of western writers with positive and negative attitudes towards Islam, based on Minou Reeves observations. After little bit of augmentation it looks as follows.
People with Positive Attitude towards Islam : (1) Roger Bacon (2) John of Segovia (3) Lessing (4) (young) Goethe (5) Boullain-Villiers (6) Bolingbroke (7) Carlyle (8) Dawson (9) Reland (10) Rilke (11) Paret (12) Sprenger (13) Tor Andrae (14) Bodley (15) Mongomery Watt (16) Rodinson (17) Annemarie Schimmel (18) Karen Armstrong (19) Edward Said (20) John L. Esposito.
Needless to mention that a list like this is neither exhaustive nor comprehensive and neither it can be, for that matter, devoid of contention. But it is certainly a very convenient guide for a beginner who would not like to reinvent the wheel.
People with Negative Attitude towards Islam : (1) Venerable Bede (d. 735 AC) (2) Chaucer(Canterbury Tales, d. 1476 AC) (3) Dante (Divine Comedy) (4) Christopher Marlowe (Tamberlaine, d. 1590 AC) (5) Martin Luther (6) Milton (7) Voltaire (8) Montesquieu (9) Diderot (10) Victor Hugo (11) Byron (12) Shelley (13) Thackeray (14) Bernard Lewis (15) Samuel Huntington.
Same comments, as earlier, should be applied here. As a parting word it should be stated that even the kindest of a westerner can not shade any light on the religion preferred by Lord Most High for us. Learn your Islam first and then have mercy on your western brothers to explain it to them. Even the best western assessment of Islam is widely off the mark. Their summary of the teachings of Islam can be very impressive (just look at BBC entries). It is the spirit of Islam that some how gets lost some where.