10. Lambent Brumak - Gears Of War 2
How you go from characters made of pure testosterone and gunpowder wielding guns with under-mounted chainsaws, to finishing on a boss that amounts to nothing more than trimming a huge weed, is beyond me.
The epic sense of scale was certainly here - as was the fantastic score - but gameplay-wise there was zero challenge, instead relegating your input to nothing more than holding the right trigger and pointing your weapon at the Brumak in question.
Keep this up for a couple of minutes with nothing else providing challenge other than the occasional tendril that might catch you unawares, forcing you to hang back for a second before resuming fire and you're done. Game complete, with a side of "Really...that was it?!"