Pärt leans towards a form of minimalism, which not everyone likes. Some of the works I personally lean towards are:
* "Cantus in memoriam Benjamin Britten": https://www.youtube.com/watch?v=bvfvO3dJqFY
* "De Profundis": https://www.youtube.com/watch?v=0vOSKaKJ1QY
* "Te Deum"† (~30m): https://www.youtube.com/watch?v=jNxbT0MESTY
* "Fratres" (for cello and piano): https://www.youtube.com/watch?v=v4XMjsYeMig
* "Fratres" (for violin and piano): https://www.youtube.com/watch?v=7PS5QMsGaRw
* "Fratres" (for violin, chambre orchestra, percussion): https://www.youtube.com/watch?v=i9I-6QPT8Is
* the Tabula rasa album: https://www.youtube.com/watch?v=7YqF69HLkj8
If you're going to listen to a choral work, it's worth looking first for recordings by the Estonian Philharmonic Chamber Choir, as Pärt often collaborates with them (sits in on performances, recordings; he's Estonian himself so there's a 'cultural collection').
† On a historical note, the "Te Deum" is one of the earliest Christians hymns we know about (and that is still used), apparently dating back to before 500 AD: https://en.wikipedia.org/wiki/Te_Deum