It's hard because most sites/services do not let you search by language or identify the language at all, people on the internet misidentify the language, and sometimes the lyrics are wrong. Also Spotify doesn't let you sort by most plays, it just shows "popular" songs, which may not be the ones with the most plays.
This is what I've come up with so far. Probably there are more popular songs than the ones listed here that I've missed, and there are languages I don't have a song for yet.
- Afrikaans: Ricus Nel - Hardekole (5.1 million)
- Albanian: Era Istrefi - Bonbon (136 million)
- Alemannic: Lo & Leduc - 079 (35.86 million)
- Amharic: Teddy Afro - Mar Eske Tuwaf (Fiqir Eske Meqabir) (2.1 million)
- Arabic (Algerian): Rachid Taha - Ya Rayah (27.81 million)
- Arabic (Egyptian): DYSTINCT - Ghazali (60.21 million)
- Arabic (Levantine): Haifa Wehbe - Touta (11.1 million)
- Arabic (Sudanese): Sharhabil Ahmed - Argos Farfish (1.91 million)
- Armenian: JANAGA - Скажи мне/Ասա դւ (2.03 million) [bilingual]
- Azerbaijani: Sami Yusuf - Nasimi (8.05 million)
- Bengali: Anupam Roy - Boba Tunnel (6.36 million)
- Bhojpuri: Samar Singh, Anta Singh Priyanka - Kamariya Ko Touch Karne Na Dungi (11.02 million)
- Bulgarian: Coby x Krisko - Nove pare (4.24 million) [bilingual]
- Burmese: Sai Htee Saing - Chit Tar Ta Khu Tae Thi Tal (492 thousand)
- Chinese (Cantonese): Beyond - 海闊天空 (45.83 million)
- Chinese (Mandarin): Teresa Teng - 月亮代表我的心 (24.1 million)
- Cornish: Gwenno - Tir Ha mor (2.30 million)
- Czech: Karel Gott & Charlotte Ella Gottová - Srdce nehasnou (9.87 million)
- Danish: Tobias Rahim & Andreas Odbjerg - STOR MAND (55.47 million)
- Dutch: Bizzey - Traag (134.78 million)
- English: The Weeknd - Blinding Lights (4.07 billion)
- Estonian: Marten Kuningas - Tagurpidi vaal (1.5 million)
- Finnish: Eppu Normaali - Vuonna '85 (13.89 million)
- French: Édith Piaf - La vie en rose (161.98 million)
- Georgian: Zviad Bekauri - მე ყოველთვის მოგცემ (1.1 million)
- German: Rammstein - Du hast (526.73 million)
- Greek: Nikos Vertis - An Eisai Ena Asteri (18.19 million)
- Gujarati: Bhoomi Trivedi - Vaagyo Re Dhol (3.57 million)
- Gumatj: Yothu Yindi - Treaty (9 million) [bilingual]
- Hebrew: Static & Ben El - אפס מאמץ (13.56 million)
- Hindi: Arijit Singh - Kesariya (476.41 million)
- Hungarian: Quimby - Autó egy szerpentinen (5.2 million)
- Icelandic: Bubbi Morthens - Rómeó og Júlía (4.03 million)
- Indonesian: Agnes Monica - Matahariku (25.45 million)
- Irish: Hozier - De Selby (Part 1) (16.72 million) [bilingual]
- Italian: BLANCO, MINA - Un Briciolo Di Allegria (68.23 million)
- Japanese: YOASOBI - 夜に駆ける (555.23 million)
- Javanese: Via Vallen - Sayang (25.75 million)
- Kannada: Sid Sriram - Jagave Neenu Gelathiye (8.38 million)
- Kazakh: Turan - Ер Тұран (5.4 million)
- Khmer: Dengue Fever - Uku (2 million)
- Korean: BLACKPINK - How You Like That (976.80 million) [bilingual]
- Kwara'ae: Stegga - Kwisi Tala Amu (120 thousand) [bilingual]
- Latvian: Apvedceļš - Zemenes (1.2 million)
- Lingala: Kanda Bongo Ban - Muchana (Zouk Love) (1.66 million)
- Lithuanian: Biplan - O mes prie jūros (1.09 million)
- Luritja: Warumpi Band - Jailanguru Pakarnu (244 thousand)
- Manam: Quakes - Lulu (10 thousand)
- Nigerian Pidgin: Fela Kuti - Water No Get Enemy (26.90 million) [bilingual]
- Norwegian: Kaizers Orchestra - Hjerteknuser (41.34 million)
- Persian: Faramarz Aslani - اگه یه روز (7.45 million)
- Pijin: Elexter Jr - Lo Honiara (325 thousand) [bilingual]
- Polish: Republika - Mamona (7.51 million)
- Portuguese: Roberto Carlos - Cama e mesa (139.89 million)
- Romanian: O-Zone - Dragostea din tei (275.88 million)
- Russian: Miyagi & Эндшпиль feat. Рем Дигга - I Got Love (129.55 million)
- Sami (Inari): Amoc - Čuđeh (163 thousand)
- Sami (Northern): Intrigue - Eadni Nieida (1.43 million)
- Scots: Steeleye Span - Cam Ye o'er frae France (1.31 million)
- Scottish Gaelic: Emma Thompson, Peigi Barker - A Mhaighdean Bhàn Uasal (16.18 million)
- Serbo-Croatian: Coby x Krisko - Nove pare (4.24 million) [bilingual]
- Slovak: Adam Ďurica - Zatancuj si so mnou (10.07 million)
- Slovene: Joker Out - Carpe Diem (20.14 million)
- Spanish: Luis Fonsi - Despacito (1.69 billion)
- Swahili: Miriam Makeba - Malaika (1.43 million)
- Swedish: Ulf Lundell - Öppna landskap (30.08 million)
- Tagalog: Lea Salonga - Bakit Labis Kitang Mahal (2.11 million)
- Tamil: Sid Sriram, Sreejith Edavana - Kaadhal En Kaviye (113.53 million)
- Thai: Bird Thongchai - รักเอ๋ย (5.10 million)
- Tok Pisin: Lista Serum - Alfie (19 thousand)
- Triqui (Copala): Carlos CGH - Los Artesanos (not on Spotify; 18 thousand on YouTube) [bilingual]
- Turkish: Sezen Aksu - Biliyorsun (68.49 million)
- Turkmen: Ka-Re - Yarala Meni (18.09 million)
- Tuvan: Huun-Huur-Tu - Ancestors (1.4 million)
- Ukrainian: SadSvit - Силуети (19.07 million)
- Uzbek: Tohir Sodiqov - Kel Yashaylik Birga (586 thousand)
- Vietnamese: Sơn Tùng M-TP - Chúng Ta Của Hiện Tại (41.59 million)
- Welsh: Daniel Pemberton - The Politics & The Life (8.29 million)
- Xhosa: Miriam Makeba - Pata Pata (35.35 million)
- Yiddish: The Barry Sisters - Chiribim Chiribom (1.32 million)
- Yoruba: Fela Kuti - Water No Get Enemy (26.90 million) [bilingual]