This would be okay for Minecraft and probably Blacklight. Guild wars 2 is more cpu demanding than it is gpu. Crysis warhead maybe high settings. You may be trying to keep it cheap, but at least try and go for something with atleast 1.5-2.0 gddr5 ram.
The 7770 is a great budget card and for $100 it's a steal. Unfortunately it's just that, a budget card. Read Tom's review and check out the benchmarks. While the 7770 is faster than the 550 Ti it doesn't scream. If you're not looking to run on Ultra then yes, it's a good deal, especially at $100.
At your resolution High settings will be easily attained, maybe Ultra / Max on the older games.
LOL I love how these always turn into "buy this not that". All the OP asked was if a Radeon 7770 for $100 was a good deal. YES. It's a smoking deal. The cheapest 7770 on Newegg is $127 ($117 after MIR).