So, I'm gonna take a more contrary view to most and say that I think Conquest should actually be in B or even C tier. To me Conquest is a good game, but it simply is not up to snuff with what is out there in its genre. Indeed, if it weren't for its Pokemon motif, it would be entirely forgettable. See, here is the thing: I don't think it is really possible to compare all these different games directly. Some people just like different types of games more, and they will naturally think them better than others. However, what I think you can more accurately compare is how good the games are in comparison to similar non-Pokemon games. When you look at things in this light, while I believe Snap and TCG and Mystery Dungeon still hold their own, Conquest becomes a lot less attractive.
I mean, Conquest is a tactical rpg, and I think that games such as that are naturally more attractive to the core Pokemon crowd. As such, I think people here have a natural inclination to see it as better than things like the D tier games. Yet, when compared to the other similar games out there (think Fire Emblem), frankly, Conquest is a mediocre at best game that uses its Pokemon facade to sell cartridges.
Don't get me wrong, I thoroughly enjoyed the game, but the point is, it is just not that great at what it is, and I find it hard to then rank it equal to or above other games that I think compare more favorably to their competition.