They all have their ups and downs, honestly I've been with Ragnarok since day1 of NA release and it will never be the top just because it's one of the originals that got messed up by mass RMT bans early. Unless you have an extremely bad wrap with your server or beef with too many players, then i wouldnt suggest jumping.
the graph shows quite a dramatic slope, i'm not too good with the whole concept of game economy...
most people who play are 75 with multiple jobs capable of most NM hunts, sky etc and crafts, does this make it more difficult for new players? the graph shows an ecominic decline, has the buying and selling of items slowed down? and have things become more expenive or cheaper?
The graph is merely a measure of average item prices, not sale rates. The extremely steep decline shows severe economic deflation, where all items become much cheaper over time. While this may sound like a universal plus, it also means that money is much more difficult to make.