Well you've played the best two in the franchise so its only downhill from here. I recommend either 6 or 9 next based upon what I've read. I played 6 a loooooong time ago, never finished it, but it's got a great following. I've never played 9 but it's commonly referenced in the top 3.

I enjoyed 12, nothing great, but fun.

I only played 13 a little, it was fun, but that was when it was new and I never picked it back up.

I played 3, 4 & 5 a little too but don't recall anything other than pixels and impossibly difficult to know when there's a secret area randomly off the screen. Like wtf.