There is no "general best" among them, everyone is best than other in some things and worse in anothers, but I believe your question must be something like "wich one is the easiest to train and use by standarth means" right? In this case the answer is staraptor and swellow in equal terms.
In the very early game Tailow/Swellow is the best, it already start with peck attack, and very soon he learn wing attack and both moves can make best use of his higher offensive stat, "Attack".
In the end of the early game, mid game and endgame, the easiest is starly/staravia/staraptor, because of looks alike terms with swellow with the exception of peck attack. Once he stabilish with wing attack in the mid-game he is already bulkier than swellow/tailow, so he is able to do the same but is also a bit bulkier and slower. But among the easiest thoose two are in almost aqual terms.
But in terms of the "best", it really doesn't have one, everybody has his strenghts and weakness and exell best than others in some unique things, things that are no better than eachother but equally important and related. For example what is best HP or speed? There is no best between thoose stats, both are important, some will be best in the hands of one than another , and is not just this, there is too many things that happen about the same quantities and are all important to be noted and not ignored. There is too many things wich one of thoose birds Pokemons can do, that can only be done by one or few than all of them. For example, can pidgeot or staraptor employ all the same as Noctowl? There are things for example that only noctow can do, there are roles that only he can fill, especially things who make good use of moves like hypnosis, dream heater, nightmare, reflect and others. Most of the others if not all of them can't even learn most of this moves to fill most roles that noctown can. But of course the others can also especialize in things that noctown or even the others beside the one in the term aren't able to, all equally important. Hope I could help it, have a nice day. :)