That's fair enough, and this is where it gets very subjective. Judging against other horses running other races to judge their sectionals can say one thing and it can say another. Is a good horse one that runs great sectionals? Or runs flat out for as long as it can? Some horses like to get cover and come late and therefore wouldn't be topping any sectionals or comparisons but would win more often than not, let's use an American horse as an example here in Zenyatta as doing such. Always a hold up horse but won every race apart from her last one - 19 out 20. Or Winx over in Australia who had a ludicrous record. I love a late-running, strong-finishing horse personally, but I also appreciate the front-running sorts like Reference Point or Dubai Millennium as well as those that seemed to cruise like your Frankels/Baaeeds/Flightlines. But winning big is just one way to win a race and some horses like to stretch out and lead and some don't, but it seems the ratings guys and Joe public get more turned on by the ones that just want to sprint to the end. It looks sexier I guess, like Frankel's Guineas win. Surely the measure of merit should be in how many times they win and the manner and significance of their wins, rather than by how much they win by.
Sure, Flightline had things easy in his career, too easy for him anyway, but much like Frankel (who did) he didn't get bigger tests to really see what he was made of, and we won't get those now. For me there are the established proven greats and then Flightline would sit in the second tier as being one of those that might well have gone on to be the best of all time, but we never got to see if that could've been the case or not because only six races and only four G1 races (only one of which was 'a big one') whilst racing up to 4 years of age should've given more. But alas, that is racing.