I think this post reflects my thoughts exactly. I keep seeing people say "oh ODST is just a 6 hour expansion"...

Wasn't CoD 4's story mode six hours (ish)

Plus ODST has the Firefight mode, which seems to be all the rage these days with developers (hell, Dawn of War 2 has a form of it)

Halo 3:ODST only takes 5 hours to pass this game on Normal/Easy mode. A lot of people do not play games much higher than Easy/Normal mode. The higher difficulty settings would increase the length of the gameplay due to enemies being more difficult to kill and you take less damage before you are killed on higher difficulty settings.
Minimum of 5 hours up to 9 hours on the most difficult setting for campaign mode.
Online Multiplayer adds a lot of replayability which more enough makes up for the short campaign mode. 21 Halo 3 maps are included plus 3 new Halo maps. New Firefight mode added to the online as well. 4 player co-op for campaign in Halo 3:ODST.

Most games get boring after finishing the campaign once through on Normal mode. Only the great games are worth playing through multiple times.

Critical review scores between 8 and 9 seem fair for this game.

Halo 3 and ODST together looks easily as long as Half Life 2 and the first 2 episodes. So I see no problem. I finsihed The Orange box in 15 hours. Halo 3 takes about 10 hours and so far Ive played 3 and half hours of ODST and am about 1/3 of the way through. Bear in mind I play all Halo games on Legendary.

^^
You played through Half Life 2, Ep 1 and Ep 2 in 15 hours? That seems a little fast, particularly if you played on harder settings.

If this was true, then why did Heavenly Sword get so critcized by gamers and reviewers for being so short dispite being of a high quality?

In the end, there has to be a cut off point as to what is too short for $60. Otherwise you are saying that you would buy a 10 minute game for $60 as long as it was high quality.

I think the criticism for ODST is it has a short campaign and repackaged Halo 3's muliplayer. It doesn't seem like a good value at $60. If you are willing to pay that, and are happy with the product, then the single player isn't too short. I paid $40 for GT5 Prologue, many of you trolled that decision saying you wouldn't pay for a demo. It's the same thing. I was happy with my purchase, and seems like Halo fans are happy with ODST. I may even buy it when it drops to the $30 range.

10+!!! I buy games for their single player experience, the longer it lasts is generally better, but the higher quality it is makes me replay it. MP adds almost nothing for me, and I hate how developers have to add multiplayer to everygame now so that people will buy it :/

An example such as the one you made that lacks common sense isn't much of an example at all. kowenicki clearly stated, "(within reason obviously)" after mentioning, "decent length". This length is determined by the game genre. An FPS can't be compared to an Adventure game in length, just an a RPG cannot be compared to a Puzzle game. Use your reasoning.

10 hours is decent. 8 hours is minimum.