Looking to get into metal slug! what are the best games/ways to do this?

[Player2]

The first one is probably the easiest one so it is a good start point. For what I've heard the third one is the best unless the sixth one have surpassed it.

The original platform of this franchise is the Neo-Geo (except for the sixth game), so your best option to play this is to get Metal Slug Antology.