Well, Archeops is a great Pokemon and is especially helpful against the later gym leaders such as Skyla and Brycen. That monstrous attack and speed mean that most Pokemon won't even get to land an attack before they get obliterated. The huge variety of attacks it gets will also allow it to fit well on your team to cover any weaknesses.
But that's about it. With its ordinary defenses and how Rock/Flying is a not being a pretty hot typing defensively, it won't be able to take more than 2 hits. But the real kicker as you already might know is its ability: Defeatist- an ability that lowers attack and sp. attack once its hp drops below half. Game Freak made sure not to let this monster of a Pokemon run wild on its own. And trust me, Defeatist is a very, very, very, very, very annoying ability. What this means is that you get hit by one attack and it's over for this poor badass mon. It's certainly not a bad choice for in-game and works pretty well for the most part.
A good flying type is Sigilyph- nice support Pokemon and great abilities. Unfezant is another good choice. It's got good attack and speed. However, according to me, the best choice is Braviary. It's a great Pokemon with decent bulk and was really a powerhouse in my White 2 team. The real problem with Braviary is that you get Rufflet really late in the game just before Elite Four.
All in all, if you really like Archeops, then sure go for it. It's an awesome Pokemon which deserves more love.
You can find a great moveset for each of these Pokemon right here at Pokemondb.
Hope I helped:)))
