Hell yeah, 4U is a great intro to the series. I started with Freedom Unite but it didn't stick. Played Tri for the wii and that's what really got me into it (which is weird cause tri is clunky as hell and I think has the least content of any mainline game).

Never really got into charge blade, but GenU did a lot of favors for my two favorite weapons at the time, great sword and gunlance, and the online bosses are absolutely nuts.

Rise is probably my favorite gameplay wise, but I prefer the pre-world armor skill system, and I'm not too keen on the Sunbreak endgame grind.

As far as old titles go, Freedom Unite is very iconic and has a ton of content, but I like portable 3rd way more. The general atmosphere of the areas and town are excellent, and it introduces Zinogre to the game so well. There's also an english patch floating around for it if you can't read japanese.