I think choosing a light voiced soprano who can pass for a boy - sort of - is one of the criteria you should look for.
Miah Persson is perfect on the Ivan Fischer.
Editia Gruberova is quite good on the Sinopoli/DG M4.
Ruth Ziesack is really good on the Danielle Gatti/Royal Phil. M4 (Conifer).
Frederica von Stade has made two recoridngs of M4, and she's quite good on both of them: Abbado/VPO (DG) and Yoel Levi/Atlanta S.O. (Telarc). By the way, the Levi/Telarc recording is a very good all-around Mahler 4 and comes with the "Songs of a Wayfarer", also sung by von Stade. It's also very inexpensive.
http://www.amazon.com/Mahler-Symphony-No-Songs-Wayfarer/dp/B00000JCIP/ref=sr_1_1?s=music&ie=UTF8&qid=1454993861&sr=1-1&keywords=mahler+4+yoel+levi+telarcElly Ameling has made two recordings also, and she's quite good on both of them: Haitink/Concertgebouw (his first one) and Previn/Pittsburgh S.O. (EMI).
These things are greatly a matter of taste, but I'm afraid I'm not crazy about Lisa della Casa on the Fritz Reinier (slightly too operatic); Dawn Upshaw on the Dohnanyi (she's too 'cutesy' with it), or the 'pipey' sounding Kathleen Battle on the highly touted Maazel/VPO (Sony) recording.
Another really excellent M4 recording is, I'm afraid, both expensive and difficult to find: Z. Macal/Czech Phil./M. Kaune (sop)/Exton (Japanese label).
http://www.sa-cd.net/showtitle/4391Whatever you do, AVOID Rene Fleming on Abbado's Berlin Phil. remake. She's fine on the Alban Berg songs, but is awful in Mahler 4.
For me, many M4's are ruined by the choice of soprano in the fourth movement. A prime example is the Litton/Dallas S.O. M4 on Delos - which is excellent in the first three movements - but is ruined in the finale by Heidi Grant Murphy.
I wasn't crazy about the Mahler remakes that Haitink made in Berlin (Philips), but
Sylvia McNair does a very good job on M4 from that series. As expected, Haitink was just a tad stodgy on that one. But he's surprisingly quite sprite-ly in his LAST M4 on the Concertgebouw's own label (RCO Live), and it features a very good soprano performance from Christine Schaefer. This one is a 'sleeper' (and I'm no great lover of Haitink).
http://www.amazon.com/Symphony-4-G-Mahler/dp/B000TKODEKOf older vintage recordings
Elsi Morison is pretty good on the Kubelik (DG);
Natalia Davrath is quite good on the Abravael/Utah S.O. M4 (Vangaurd), and
Reri Grist is excellent on the old Bernstein/N.Y./Columbia (Sony) M4.
Edith Mathis is a tad matronly, but quite good on the Karajan. She also appears on the Bernstein/V.P.O. dvd of M4, which is coupled to decent performances of M5 and M6.
http://www.amazon.com/Mahler-Symphonies-Leonard-Bernstein-Philharmoniker/dp/B000AC5BES/ref=pd_sim_74_1?ie=UTF8&dpID=517UcFmOfLL&dpSrc=sims&preST=_AC_UL160_SR120%2C160_&refRID=1W3Z0A6KAC236Q221JWBAnd if you actually want to hear a true 'boy treble' sing the part, Bernstein employed one on his Concertgebouw re-make on DG.
http://www.amazon.com/Mahler-Symphony-No-Helmut-Wittek/dp/B000001G9E/ref=sr_1_2?s=music&ie=UTF8&qid=1454994402&sr=1-2&keywords=mahler+4+bernstein+deutsche+grammophonIt's interesting, but a boy does struggle with the 'gymnastics' of Mahler's writing.