Price/value wise it's a fair trade. The new GOTG code is much better than it was, so it's not a bad game, and there is value to a brand new shiny game verses a 15 year old game. Bottom line is you won't be losing any money/value on the trade.
It's always tough to "let go" of a great game, but we only have room for so many and it's fun to try out different games.