Here are the ways to say "I love you" in many languages.
LANGUAGE
I LOVE YOU
COMMENTS
Afrikaans Ek het jou liefe
Ek is lief vir jou
Albanian te dua
te dashuroj
Alentejano Gosto De Ti, Porra! Portugal
Alsacien Ich hoan dich gear
Amharic Afekrishalehou
Arabic Ana Behibak (to a male)
Ana Behibek (to a female)
Ib'n hebbak.
Ana Ba-heb-bak
nhebuk
Ohiboke (male to female)

Ohiboka (female to male)

Ohibokoma (male or female to two males or two females)

Nohiboke (more than one male or female to female)

Nohiboka (male to male or female to male)

Nohibokoma (m. to m. or f. to two males or two females)

Nohibokom (m. to m. or f. to more than two males)

Nohibokon (m. to m. or f. to more than two females)

(not standard) Bahibak (female to male)

(not standard) Bahibik (male to female)

(not standard) Benhibak (more than one male or female to male)

(not standard) Benhibik (male to male or female to female)

(not standard) Benhibkom (m. to m. or female to more than one male)
Armenian Siroum em kez Thanks Mike
Assamese Moi tomak bhal pau
Basc Nere Maitea
Batak Holong rohangku di ho
Bavarian I mog di narrisch gern
Bengali Ami tomAy bhAlobAshi
Ami tomake bhalobashi.
Berber Lakh tirikh
Bicol Namumutan ta ka
Bolivian Quechua qanta munani
Bulgarian Obicham te
Burmese chit pa de
Cambodian a.k.a. Khmer Bon sro lanh oon
kh_nhaum soro_lahn nhee_ah
Canadian French Sh'teme (spoken, sounds like this)
Cantonese Moi oiy neya
Ngo oi ney
Chinese
Catalan T'estim (mallorcan)
T'estim molt (I love you a lot)

T'estime (valencian)

T'estimo (catalonian)
Cebuano Gihigugma ko ikaw.
Chickasaw chiholloli (first "i" nasalized) American Indian
Chinese (see the entries for mandarin or cantonese!)
Corsican Ti tengu cara (to female)
Ti tengu caru (to male)
Creole (Haitian) Mwen renmen ou.
The "en" is pronounced as the French "in" nasal sound.
The "ou" is pronounced as in the French "ou" or the English "oo".
Thanks to Dan
Croatian & Serbian Ljubim te "means to kiss you"
Ya te volim "I love you"

or

Volim te "I love you"
Thanks to tanya karlovic for corrections
Czech miluji te
MILUJU TE! (colloquial form)
Danish Jeg elsker dig
Dutch Ik hou van jou
Ik ben verliefd op je
Ecuador Quechua canda munani
English I love you
Esperanto Mi amas vin
Estonian Mina armastan sind
Ma armastan sind
Farsi Tora dust midaram
Asheghetam

(Persian) doostat dAram
Filipino Mahal ki ta
Iniibig Kita
Finnish Mina" rakastan sinua
Flemish Ik zie oe geerne
French Je t'aime

Je t'adore

Friesian Ik hald fan dei
Gaelic Ta gra agam ort
German Ich liebe Dich
Greek s'ayapo (spoken s'agapo, 3rd letter is lower case'gamma')
(old) (Ego) philo su (ego is only needed for emphasis)
Greenlandic Asavakit
Gujrati Hoon tane pyar karoochhoon.
Hausa Ina sonki
Hawaiian Aloha wau 'ia oe
Hebrew Ani ohev otach (male to female)
Ani ohev otcha (male to male)

Ani ohevet otach (female to female)

Ani ohevet otcha (female to male)
Hindi Mai tumase pyar karata hun (male to female)
Mai tumase pyar karati hun (female to male)
Main Tumse Prem Karta Hoon
Mai Tumhe Pyar Karta Hoon
Main Tumse Pyar Karta Hoon
Mai Tumse Peyar Karta Hnu
Mai tumse pyar karta hoo
Hokkien Wa ai lu
Hopi Nu' umi unangwa'ta American Indian
Hungarian Szeretlek
Szeretlek te'ged
Icelandic Eg elska thig
Indi Mai Tujhe Pyaar Kartha Ho
Indian Meitei Language Ei Nungbu Nungshi (I love You}
Ei nungbu yamna nungshi (I love you a lot)
Courtresy of Sanahal Y.
Indonesian Saya sayang padamu (Saya, commonly used)
Saya cinta kamu

(Aku is used more commonly among the younger generations)
Aku sayang padamu

Aku cinta kamu
Courtresy of V.
Iranian Mahn doostaht doh-rahm
Irish taim i' ngra leat
Italian ti amo (if it's a relationship/lover/spouse)
ti voglio bene (if it's a friend, or relative)
Japanese Kimi o ai shiteru
Aishiteru

Chuu shiteyo

Ora omee no koto ga suki da

Ore wa omae ga suki da

Suitonnen

Sukiyanen

Sukiyo

Watashi Wa Anata Ga Suki Desu

Watashi Wa Anata Wo Aishithe Imasu
Watakushi-wa anata-wo ai shimasu
Suki desu (used at 1st time, like for a start, when you are not yet real lovers)
Javanese Kulo tresno
Kalenjin Achamin
Kannada Naanu Ninnanu Preethisuthene
Naanu Ninnanu Mohisuthene
Kiswahili Nakupenda
Korean No-rul sarang hae (man to woman in casual relationship)
Tangsinul sarang ha yo
Tangshin-ul sarang hae-yo
Tangsinul Sarang Ha Yo
Tangshin-i cho-a-yo (i like you, in a romantic way)
Nanun tangshinul sarang hamnida
Nanun Dangsineul Mucheog Joahapnida
Nanun Dangsineul Saranghapnida
Nanun Gdaega Joa
Nanun Gdaereul Saranghapnida
Nanun Neoreul Saranghanda

Gdaereul Hjanghan Naemaeum Alji

Joahaeyo

Saranghae

Saranghaeyo

Saranghapanida
Kurdish Ez te hezdikhem (?)
Lao Koi muk jao
Khoi huk chau
Latin Te amo
Vos amo

(old) (Ego) amo te (ego, for emphasis)
Latvian Es milu tevi (Pronounced "Ess tevy meeloo")
Lebanese Bahibak
Lingala Nalingi yo
Lisbon lingo gramo-te bue', chavalinha
Lithuanian TAVE MYLIU (ta-ve mee-lyu)
Lojban mi do prami
Luo Aheri
Macedonian TE SAKAM! Thanks Marija
Madrid lingo Me molas, tronca
Malay/ Indonesian Saya sayang padamu (Saya, commonly used)
Saya cinta kamu

(Aku is used more commonly among the younger generations)
Aku sayang padamu

Aku cinta kamu
Malayalam Njyaan Ninne' Preetikyunnu
Njyaan Ninne' Mohikyunnu.

Ngan Ninne Snaehikkunnu
Malaysian Saya Cintamu
Saya Sayangmu
Saya Cinta Kamu
Mandarin Wo ai ni (Wo3 ai4 ni3 in tonal notation) Chinese
Marathi me tujhashi prem karto (male to female)
me tujhashi prem karte (female to male)
Mi tuzya var prem karato
Mohawk Konoronhkwa American Indian
Navaho Ayor anosh'ni American Indian
Ndebele Niyakutanda
Norwegian Eg elskar deg (Nynorsk)
Jeg elsker deg (Bokmaal) (pronouncedyai elske dai)
Op Op Lopveop Yopuop
Pakistani Mujhe Tumse Muhabbat Hai
Persian Tora dost daram
Pig Latin Ie Ovele Ouye
Polish Kocham Cie
Ja cie kocham

Yacha kocham

Kocham Ciebie
Portuguese Amo-te
(brazilian) Eu te amo
Punjabi Mai taunu pyar karda
Main Tainu Pyar Karna
Quenya Tye-mela'ne
Romanian Te iu besc
Te Ador
Russian Ya vas liubli
Ya tebya liubliu
Ya polubeel s'tebya

(malincaya) Ya Tibieh Lublue
Scot Gaelic Tha gra\dh agam ort
Serbian Ya te volim "I love you"
or
Volim te "I love you"
Thanks to tanya karlovic for corrections
Serbocroatian Volim te
Ljubim te
Shona Ndinokuda American Indian
Sinhalese Mama oyata adarei
Sioux Techihhila American Indian
Slovak lubim ta
Slovene ljubim te
Somali kujali
Spanish Te amo
Srilankan Mama Oyata Arderyi
Swahili Naku penda (followed by the person's name)
Swedish Jag a"lskar dig
Swiss - German Ch'ha di ga"rn
Syrian/ Lebanese BHEBBEK (to a female)
BHEBBAK (to a male)
Tagalog Mahal kita Phillipines
Tahitian Ua Here Vau Ia Oe
Tamil Ni yaanai kaadli karen (You love me)
n^An unnaik kAthalikkinREn (I love you)

Naan Unnai Kadalikiren
Tcheque MILUJI TE^
Telugu Neenu ninnu pra'mistu'nnanu
Telugu/ india Nenu Ninnu Premistunnanu
Thai Phom Rak Khun (formal, male to female)
Ch'an Rak Khun (formal, female to male)
Khao Raak Thoe (affectionate, sweet, loving)
Phom Rak Khun
Tunisian Ha eh bak *
Turkish Seni seviyo*rum (o* means o)
Seni Seviyurum

Seni Seviyorum
Turkmen Men seny soyarin
Ukrainian ja tebe koKHAju (real true love)
ja vas koKHAju
ja pokoKHAv tebe
ja pokoKHAv vas
Urdu Mujhe tumse mohabbat hai
Main Tumse Muhabbat Karta Hoon
Uzbek Man seni sevaman
Vietnamese Em ye^u anh (woman to man)
Toi yeu em
Anh ye^u em (man to woman)
Vlaams Ik hou van je
Ik zie je graag
Thanks Thierry Boeve for correction!
Welsh 'Rwy'n dy garu di.
Yr wyf i yn dy garu di (chwi)
Yiddish Ich libe dich
Ich han dich lib
Ikh Hob Dikh Lib
Yugoslavian Ja te volim
Zazi Ezhele hezdege (sp?)
Zulu Mena Tanda Wena
Ngiyakuthanda!
Tom ho' ichema