Well, opinions will always be varied and sometimes a little eccentric.. one thing you can definitely count on is Hector being one of (and some will say THE) best characters in the game. Some (such as myself) love magic units and so good magic units get placed at higher ranks on a ''best'' list than physical units. Other characters can vary between being some of the best and some of the worst, many of which are extremely sensitive to the RNG. If you go to the GameFAQs forums (and probably places around here too), there will be people who tell you that Lyn is one of the worst Lords ever, and she's just a crappy Lord. In my (at least) 10+ playthroughs of FE7.. I've never had a horrible Lyn. She's one of my favorite units, and always ends up being a killer lord.. far better than Eliwood.
That said... Here's a more detailed list I suppose?
Hector (FE7): He has great stat growths and pretty damn good stat caps after promotion. He can wield Armads, which is a plus.. and hey.. he can used Swords after promotion too. With the exception of the final chapter.. I can toss Hector into any map, with hordes and hordes of enemies of varying classes.. and they'll just kill themselves on him. Hector is a God in pixel form. Spartans based their culture and war tactics around tales of his exploits.
Oswin (Fe7): The General is an amazing class. Sure, not so hot on the movement.. but it is the medieval equivalent to the tank. Except better. (In FE8, but I'm sure in FE7 as well) It boasts the highest total stat caps of any normal playable class in the game, and Oswin fills this role quite nicely. I've never had a bad Oswin.. and many will agree that Oswin comes close to being as godly as Hector. A great class, a great character.
Fil (FE6): A lot of people don't like the Swordmaster class. I do. I never beat FE6, but man.. Fil was pretty dang good, and a glance at the character comparison FAQ on GameFaqs shows I wasn't just the only one. She's like Joshua for FE6... except female. Her STR growth is just as good, if not better (might be better? Haven't checked. My Joshuas almost always near cap STR).. and that's almost always a stat they're low in. Swordsmasters with high Str = a Win in my book.
Raven (FE7): Raven's another godly character. If Hector is a 10 out of 10, Raven's probably a 8 to 9 out of 10. The Hero class has great stat caps, and Raven can fill them in pretty darn nicely.
Dieck (FE6): Probably my favorite FE6 character, as he's the one I got furthest with. He'll end up a Hero, like Raven.. but my Dieck ended up a lot better than my Ravens did.
Dart (FE7): You don't get many pirates. Luckily, Dart is one hell of a pirate. Might be a little issue in leveling him up without dying initially, but he turns into a superb unit especially after promotion into Berserker. His biggest drawback is, of course, his defense.. but he does such high damage and swings at such great speeds... he'd bust his enemies skull twice before they even got the chance to hit him. That is, assuming, the skull is still intact from his first strike.
Rebecca (FE7): As a Sniper, Rebecca does a fantastic job of dealing good damage, double-striking, and dodging enough to stay alive. Archers aren't a great class in my opinion.. but unless I'm doing some sort of special playthrough, Rebecca is a staple in my army.
Lucuius (FE7): Possibly one of the best magical units ever. He will probably max Mag. He will max Skl, he will probably max Spd, and he will definitely max Res (mine always has anyway). No magic units will ever stand up to Lucius. Period. Period. Had to add some extra emphasis. He must be related to Hector, because there's no way such a nice and warm-hearted man of the Church could be such a God of Magical Combat. The Bishop class is a limit on Lucius ability.. but he has great utility in being able to attack close-range, long-range, as well as use staves to heal and support his allies. A recommended unit.
Nino (FE7): Since you said you don't care about recruitment levels and whatnot. Nino's probably the best magic user of FE7. Some people have had an issue with her not capping magic. Maybe I'm just RNG blessed.. but very rarely is she more than 2-3 points away from capping at... and that's when I consider her RNG screwed. She's like a magical Hector.. I can toss her out into pretty much whatever map I choose, and enemies just kill themselves on her. The Sage class is my personal favorite.. Anima magic is magnificent and it's always nice to be able to have a healer who can fight whenever needed.
And I will stop now.. because this is getting a bit long.