As exposed in my Singin' To English book, singing to English is a great exercise to practise your English in many ways... if lyrics are selected appropriately...
For the discerning fan there is a wealth of songs to choose from... in most styles too...
Still... ABBA, Boney M, Alison MOYET (including her Yazoo period), the Bee Gees especially Main Course, Children Of The World & Spirits Having Flown and those including their albums for Diana ROSS, Barbra STREISAND, and Dionne WARWICK), Rupert HOLMES, Amanda LEAR (especially her I Am A Photgraph, Sweet Revenge, Never Trust A pretty Face & Tam-Tam),
In other languages I recommend
Biagio ANTONACCI, Lucio BATTISTI (up to Una Giornata Uggiosa), Loredana BERTÈ, Luca CARBONI, Riccardo COCCIANTE, Toto CUTUGNO, Lucio DALLA, Ivano FOSSATI, Matia Bazar, Romina POWER & Al Bano, Ricchi E Poveri, Roberto VECCHIONI, Renato ZERO (Zerofobia, Zerolandia & Ero Zero)
Marie-Paule BELLE, Michel BERGER, Christophe, Clarika, Joe DASSIN, France GALL, Michel JONASZ, Maxime Le FORESTIER, Claude NOUGARO, Michel POLNAREFF, Serge REGGIANI, Alain SOUCHON, Laurent VOULZY
Herbert GRONEMEYER, Ute LEMPER, Silly
Azucar Moreno, Miguel BOSÈ, Gloria ESTEFAN, Jeanette, Meccano, Ana TORROJA,
ABBA (and ABBA members and friends) Swedish albums, Marie FREDRIKSSON, Carola HÄGGKVIST, Lisa NILSSON, Mauro SOCCO
All these suggestions are ply the beginning... of course !