Yes but a megadrive did not fit in your pocket, and the game gear, while backpackable, had awful battery life. The smartphone is successful running game gear level games because it will do so all day, and has a setup time of four seconds from impulse to game.
Plus the game gear was more a master system than a megadrive even if both would run columns (I was wondering if ppl from the US understand what a megadrive is since I think they call it genesis).
Talking about battery life, I had a lynx which was even worse I think.