How many paintings called "The Last Supper" do you know?
If you are like most people*, including the well educated, then you know of one!
*Art history majors, art fanatics and theologians excl.

The Last Supper (1498)
by the great Leonardo Da Vinci

However, just as the last supper is not about one man eating dinner by himself, Da Vinci is not the only one who has painted the event. In fact - he is not even the first one! Nor the last one...
And just as Jesus is the most famous character in "The Last Supper" painting, Leonardo Da Vinci is the most famous artist of all "The Last Supper" artists.
The Last Supper Collection
Here is a small excerpt of the best Last Supper paintings, including only those painted within 2 centuries before & after Leonardo da Vinci, so roughly from 1300 until 1700. The paintings represent a scene from the Gospel according to John in which Jesus shares his last meal with his 12 apostles and disciples.

Duccio di Buoninsegna, 1311

Andrea del Castagno, 1450

Dirk Bouts, 1467

Cosimo Rosselli, 1480

Domenico Ghirlandaio, 1486

Leonardo Da Vinci, 1498

Andrea del Sarto, 1525

Hans Holbein, 1525

Jacopo Bassano, 1542

Tintoretto, 1594

Alonso Vázquez, 1603

Simon Vouet, 1620

Rubens, 1621

Daniele Crespi, 1625

Valentin de Boulogne, 1626

Philippe de Champaigne, 1648
Why Da Vinci's "The Last Supper"?
This is quite an impressive collection of paintings, yet none of them is as well known as Da Vinci's. So, why is that?
What makes Leonardo's Last Supper the one we have all heard of?
In short:
It used a new painting technique (painting on dry plaster instead of wet plaster, which was the traditional technique). Unfortunately this is also the reason for the deterioration of the painting, which began only a few years after it was completed. Jesus isn't decorated with a halo. While this is not the first painting to depict Jesus without a halo (see Bouts, 1467), it was common practise, at the time, to include it. It clearly shows the reaction of each of the apostles as Jesus announced that one of them will betray him. It is mathematical in nature, with musical properties ("resonance between visual and aural harmonies"). It seems you have the right viewing position regardless of where exactly you view it from.
In our time two books have brought additional attention to Leonardo's work. Those books are:
1. "The Templar Revelation" (1997), by Lynn Picknett and Clive Prince, and
2. "The Da Vinci Code" (2003), by Dan Brown