Well - maybe you're not using the same version of MAME that was used to make the recordings. Sometimes that matters and other times it doesn't.(posted 9996 days ago)If you look at the tables for spiders you'll see that all the top 3 recordings were made with m33b5. Vince's cclimber recording was made with the official mame31 release.
In case you don't have copies of these old MAME binaries, I keep a page of all the DOS versions of MAME with the record/playback feature on http://guruchoc.communitech.net/zwaxy/diffs.htm - you can get to it by clicking 'Index' on the top line, then 'versions' in middle of the bottom line of the table on the index page.
I hope that helps...
Chris.