TS2 is praised quite highly because it's both difficult and fun. it's quirky, interesting, and just the kind of game to chill and have a good time with. TS3 isn't as fun and takes a more serious tone, which... doesn't fit as well as 2 as a result.
TS4 being shopped around in 2008 doesn't surprise me as a problem - Crysis 1 was MUCH more ambitious than Crysis 2. the specs on some games you see in 2008 FPS are ridiculous for PC as well, look at Vegas 1 or Crysis 1 (same specs as Vegas 2, higher specs than Crysis 2). optimization happened in the following years and prices should've dropped notably as well. still not CHEAP, but certainly managable. if you want something extremely ambitious you will have problems, but games like Demon's Soul were financially successful, let alone the sequel, and it looks good enough. if they tried to shop it around now they probably would have much less issues and they'd have a notably bigger base with the sharp increase in PC gaming as well.
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The King Wang.
Listen up Urinal Cake. I already have something that tells me if I'm too drunk when I pee on it: My friends. - Colbert.