Its hard to find good quality versions of the originals especially the more older stuff. You just have to keep searching & comparing . A few examples of songs that are hard to find in good audio quality: Sweet Caroline [Neil Diamond], You aint seen nothin yet [BTO], Unchained Melody [Righteous Brothers], I only want to be with you [Dusty Springfield], ...
Generally i go for the originals rather than remakes when i can find good quality audio; a few exceptions: Gambler [Kenny Rogers, i like the instrumentation backing of the re release], I'm into something good [Hermans Hermits , a few remakes around listen first], Lets twist again [Chubby Checker, my original isnt top notch thats why]...