The "last month" stats from http://moneroblocks.info/stats shows 0.67 transactions per block on average, which equates to about 0.3 transactions a minute, since Monero has had two minute blocks for a few months now.
Based on the historical Bitcoin transaction rate posted by lethos3, Bitcoin averaged an equivalent rate of 3 transactions per (10 minute) block in early 2011, even late 2010.
The stats on moneroblocks.info show the average number of transactions to be relatively constant (last yeat shows 0.42 transactions per block, but a good amount of that year was spent with a minute between blocks).
The last spam attack on Monero was in 2014, so this is not a concern when comparing this page's stats with Bitcoin. One thing which might make some difference is that many people seem to have difficulty using simplewallet, and will thus either eschew Monero, or keep their coins on an exchange, despite the risks involved. The subset of those people who actually trade will therefore not have transactions to and between exchanges. Some people have stated they expect usage to pick up once the monero core GUI wallet is out.